University of Groningen

Tuning of the luminescence in poly((silanylene)thiophene)sHerrema, Jan Karst

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T

thiophene 2-thienyl 2,2'-bithienyl or2,2'-bithiophene

2,2':5',2"-terthiophene

5,5'''-dibromo-3,3"'-dibutyl-2,2':5',2":5'',2'''-quaterthiophene

1

5

4 3/

2/α

β

SS S

S

Bu

Bu

BrBr

S S

5

4 3

2

5'

3' 4'

2'

2"

3" 4"

5"S

S S

5

4 3

25'

3' 4'

2'

SS

5

4 3

2

5'

3' 4'

2'

2"

3" 4"

5"

5'''

3''' 4'''

2'''

Figure A1.1

T

Nomenclature and short-hand notation

A1.1 NOMENCLATURE

he main purpose of chemical nomenclature is to identify a chemical species. Itshould additionally contain within itself an explicit or implied relationship to the

structure of the compound. This purpose requires a system of principles and rules, theapplication of which gives rise to a systematic nomenclature. During the writing of ourfirst report on copolymers of alternatingσ-conjugated silanes andπ-conjugatedthiophene blocks1 we chose as a semi-systematic name for these compounds:poly[(silanylene)thiophene]s. Since the first report on poly[(silanylene)thiophene]s byHu and Weber2 almost a dozen studies have been reported.3 Various authors usedifferent names for the same polymers. For example, poly[(dimethylsilylene)thiophene](p-TSiMe2, 5.1a, Herrema and coworkers) is called poly[2,5-(dimethylsilylene)-thienylene] (Ohshita and coworkers), poly(2,5-thienylene dimethylsilylene) (Yi andcoworkers), and poly[2,5-thiophenediyl(dimethylsilylene)] (Park and coworkers). Forthis reason a brief survey of the relevant nomenclature on the oligomers, cyclics andcopolymers presented in this thesis is given in the next paragraph.

Thiophene and oligothiophenes4,5

he nomenclature and numbering of thiophene and bi- and polythienyls is generallyagreed upon and some basic compounds used in this thesis and their IUPAC

names are shown in Figure A1.1. Instead of bi-, ter-, quater-, quinque-, sexithienyl etc.also the term oligothiophenes is extensively used and will appear in this thesis, mainlybecause the polymer is called poly(thiophene). The numbering of the positions isillustrated in Figure A1.1 for compounds up to a quaterthiophene. If more rings are

Nomenclature and short-hand notation

132

B

trimethylsilyl pentamethyldisilanyl

tetramethyldisilanylenedimethylsilylene

hexamethyldisilane

SiMe

MeMe

SiMe

MeSiMe

MeSiMe

Me

SiMe

MeMe Si

Me

Me

SiMe

MeMe Si

Me

MeMe

Figure A1.2

T

involved, this becomes cumbersome. However, in this thesis, and in general foroligothiophenes longer than terthiophene, only compounds with the rings connected viathe 2- and 5-positions, i.e., theα-positions, will be described. The name of, forexample 2,2':5',2''-terthiophene may be simplified to terthiophene.

Silanes4,6

y definition an organosilicon compound is one containing at least one organicgroup attached to silicon directly through carbon. The rules of nomenclature

according to the IUPAC for compounds and/or substituents of organosilicon chemistryused in this thesis are given below and some of them are outlined in Figure A1.2.(1) Silanes.The compounds having the general formula Me3Si[SiMe2]nSiMe3 will becalled permethyldisilane, trisilane, etc. according to the number of silicon atoms presentand are named analogously to the corresponding hydrocarbons.(2) Radicals.The following names of radicals containing silicon are adopted:

Silyl H3Si-Silylene H2Si=Disilanyl H3Si-H2Si-Disilanylene -H2Si-H2Si-

The abbreviated form 'silyl' is used instead of 'silanyl' in order to distinguish betweentwo silyl groups, 'disilyl', and one 'disilanyl' group, without using the multiplicativeprefix 'bis-'.(3) Hydroxy derivatives. Hydroxyl groups attached to a silicon atom will be namedadding the suffixes ol, diol etc. to the name of the parent compound:

Silanol H3SiOH

Organic Polymers and Copolymers7

raditionally, polymers have been named by attaching the prefix 'poly' to the nameof the real or assumed monomer from which it is derived. Emphasis in 'modern'

organic polymer nomenclature8 is directed to the structure of the macromolecule. Thisnomenclature adheres as much as possible to the rules for the nomenclature of organicchemistry. This structure-based nomenclature describes chemical structures rather thansubstances.

Appendix 1

133

poly[5,5'-(2,2'-bithienylene)-alt-1,1,2,2-tetrabutyldisilanylene]

poly[5,5'''''-(4',3''''-dioctyl-α−sexithienylene)-alt-dimethylsilylene]

n

S

SSi

Bu

Bu

Si

Bu

Bun

S S

S SS

S

Oct

Oct

Si

Me

Me

Figure A1.3

T

Copolymers are polymers that are derived from more than one species ofmonomer.9 Irrespective of the synthetic route used for the copolymers presented in thisthesis, the polymers all have an alternating arrangement of two monomeric subunits,an oligothiophene (oligothienylene) unit and a sil(an)ylene unit, respectively. Becausethese polymers have constitutionally regular structures and are regular polymers, thenomenclature for single-strand organic polymers is applicable.10 This nomenclature isbased on the use of the constitutional repeat unit (CRU). Copolymers described in thisthesis have a constitutional repeat unit containing two subunits. Order of seniority ofthe subunits is (1)heterocyclic rings; followed by (2)chains containing heteroatoms;(3) carbocyclic rings; and (4) chains containing only carbon. Groups having fixednumbering retain that numbering in naming the CRU. The use of these IUPAC rulesapplied to the copolymers presented in this thesis is illustrated in Figure A1.3. Thequestion of the careful reader might be why the copolymers described in this thesis stillhave the name poly[(silanylene)thiophene]s. The semisystematic name originallychosen became a trivial name for us.

Silathiophenophanes

hiophenophanes are part of the large family of 'phane' compounds. The termphanes applies to cyclic systems consisting of ring(s) or ring system(s) having the

maximum number of noncumulative double bonds connected by saturated and/orunsaturated chains. IUPAC rules for cyclophanes are rather complicated. Anindependent system of nomenclature was introduced by Cram11 and subsequentlysystematized by Schubert,12 Smith13 and extended by Vögtle and Neumann.14

The prefix 'cyclo' stands for the benzene ring, which is most commonly present inexamples of phanes. Simple names like anthracene, pyrrole, thiophene etc. are the basisfor the nomenclature of bridged aromatics which is the advantage over the IUPACnomenclature. The lengths of the bridges in a phane are placed in order of decreasing

Nomenclature and short-hand notation

134

SS

S SiSi

Si SS

S Si

1,1,1',1',2,2,2',2'-octabutyl-1,1',2,2'-tetrasila[2.2](9,20)α,α'-terthiophenophane(phane nomenclature)

10,10,11,11,24,24,25,25-octa-n-butyl-29,30,31,32,33,34-hexathia-10,11,24,25-

tetrasilaheptacyclo[24.2.1.12,5.16,9.112,15.116,19.120,23]tetratriaconta-2,4,6,-

8,12,14,16,18,20,22,26,28-dodecaene (IUPAC nomenclature)

or

Figure A1.4

T

length in square brackets in front of the name e.g. [2.2]cyclophane. Positions of thebridges can be designated byortho, meta, para,or with numbers in parentheses as inthe case of thiophene, e.g. [2.2](2,5)thiophenophane. The phane nomenclature is easilyapplicable to most compounds, from relatively simple phanes to more complicatedstructures. From the name one easily recognizes the basic structure, connectingpositions, and lengths of the bridges as is illustrated in Figure A1.4 for asilaterthiophenophane described in Appendix 2.

A1.2 SHORT-HAND NOTATION USED FOR THE COMPOUNDS IN THIS THESIS

he short-hand notation used in this thesis is outlined in Figure A1.5. In the caseof alkyl-substituted oligothiophenes, for example T6Bu2, this notation does not give

an unambiguous assignment of the position of the butyl groups. This is a disadvantagebut a full assignment in the case of T6Bu2 should include the positions 4' and 3'''' andthis does not give the reader a direct clear indication of the positions either. Above all,for T16Oct8 this again becomes cumbersome. For all the compounds described in thisthesis the short-hand notation used for a specific compound is unique.

Appendix 1

135

1. Wildeman, J.; Herrema, J.K.; Hadziioannou, G.; Schomaker, E.J. Inorg. Organometal.Polym.1991, 1, 567.

2. Hu, S.; Weber, W. P.Polym. Bull.1989, 21, 133.3. (a) Ohshita, J.; Kanaya, D.; Ishikawa, M.; Koike, T.; Yamanaka, T.Macromolecules1991,

24, 2106. (b) Ohshita, J.; Kanaya, D.; Ishikawa, M.Appl. Organomet. Chem.1993, 7, 269.(c) Ohshita, J.; Kanaya, D.; Ishikawa, M.J. Organomet. Chem.1994, 468, 55. (d) Chicart,P.; Corriu, R.J.P.; Moreau, J.J.E.; Garnier, F.; Yassar, A.Chem. Mater.1991, 3, 8. (e)Ritter, S.K.; Noftle, R.E.Chem. Mater.1992, 4, 872. (f) Yi, S. H.; Nagase, J.; Sato, H.Synth. Met.1993, 58, 353. (g) Park, J.; Choi, J.H.; Cho, S.; Chang, T.Polymer1993, 34,3332. (h) Fang, M-C.; Watanabe, A.; Matsuda, M.J. Organomet. Chem.1995, 489, 15. (i)Herrema, J.K.; Hutten, P.F. van; Gill, R.E.; Wildeman, J.; Wieringa, R.H.; Hadziioannou,G. Macromolecules1995, 28, 8102.

T T2

T3

T6Bu2

TxSi2Me5 Me3SiTxSiMe3T[SiMe2]yT

p-TxSiyR2y

[TSiMe2]4

z=0 : T4Oct2z=1 : T8Oct4z=2 : T12Oct6z=3 : T16Oct8

SS S

SSS

SS S

S

Bu

Bu

SS

S S

Me

Me

SSi Si Me

Me

Me

Me

SSi Si Me

Me

z

SS

S SS

SS S

OctOct

OctOct

x xy

Si Si

Me

Me

Me

Me

Me

SH

Me

Me

S SSi Si

Me

Me

MeS

Si

Me

Me

Me

y

R

R

SiS

xN

Figure A1.5 Overview of some selected compounds studied and the nomenclature used.

A1.3 REFERENCES

Nomenclature and short-hand notation

136

4. Panico, R.; Powell, W.H.; Richer, J. (eds.),A Guide to IUPAC Nomenclature of OrganicCompounds, Recommendations 1993, Blackwell Scientific Publications, Oxford, 1993.

5. Gronowitz, S. (ed.),The Chemistry of Heterocyclic Compounds, Volume 44: Thiophene andits Derivatives, Part 5, John Wiley & Sons, Inc., 1993.

6. Eaborn, C.Organosilicon Compounds, Butterworths Scientific Publications, London, 1960.7. Metanomski, W.V. (ed.),Compendium of Macromolecular Nomenclature, Blackwell

Scientific Publications, Oxford 1991.8. IUPAC, Pure Appl. Chem.1976, 48, 373.9. IUPAC, Pure Appl. Chem.1974, 46, 477.10. IUPAC,Pure Appl. Chem.1985, 57, 1427.11. Cram, D.J.; Steinberg, H.J. Am. Chem. Soc.1951, 73, 5691.12. Schubert, W. M.; Sweeney, W. A.; Latourette, H. K.J. Am. Chem. Soc.1954, 76, 5462.13. Smith, B. H.Bridged Aromatic Compounds,Academic Press, New York, 1964.14. (a) Vögtle, F.Tetrahedron Lett.1969, 3193. (b) Vögtle, F.; Neumann, P.Tetrahedron Lett.

1970, 5847.

Octabutyltetrasila[2.2]terthiophenophaneJan K. Herrema, Jurjen Wildeman, Fré van Bolhuis and Georges HadziioannouActa Crystallographica 1994, C50, 1112.

Crystal structureof

Octabutyltetrasila[2.2](5,5")terthiophenophane

ABSTRACT

The title compound, 1,1,1',1',2,2,2',2'-octabutyl-1,1',2,2'-tetrasila[2.2](9,20)-, '-terthiophenophane (10,10,11,11,24,24,25,25-octa-n-butyl-29,30,31,32,-

33 ,34 -hexa th ia -10 ,11 ,24 ,25 - te t r as i l ahep tacyc lo [24 .2 .1 .12,5. -16,9.112,15.116,19.120,23]tetratriaconta-2,4,6,8,12,14,16,18,20,22,26,28-dodecaene,C56H84S6Si4) provides the first example of the crystal structure of a[2,2]thiophenophane bridged by silanes. The molecule is centrosymmetric.All the thiophene rings are nearly planar.

Octabutyl[2.2]tetrasilaterthiophenophane

138

AA2.1 COMMENT

s part of our studies of the synthesis and structure ofpoly[(silanylene)thiophene]s, we recently reported the isolation of cyclic

compounds as by-products in the synthesis of the copolymers.1 These cycliccompounds consisting ofσ-π conjugations, are of interest because of their specialelectronic and chemical properties. A few X-ray data on paracyclophanes have beenreported and although the photoelectron spectrum of octamethyltetrasila[2.2](2,5)-thiophenophane was reported,2 no crystal structure of a thiophenophane bridged bypolysilanes has been reported until now. The title compound (I) is a by-product ofthe synthesis of a polymer which we are studying as the active layer inlight-emitting diodes.3

Figure A2.1 PLUTO drawing illustrating the configuration and the atom-numbering scheme

The triclinic unit cell contains only one molecule; this molecule has a centre ofsymmetry. The thiophene rings are nearly planar (to within 0.012 ) and adjacentrings lie in an antiparallel orientation. The angles between the least-squares planethrough atoms S2, C13, C14, C15, C16 and the planes of S1, C9, C10, C11, C12and S3, C17, C18, C19, C20 are 8.1(9) and 7.7(9)°, respectively. These valuescompare well with the torsion angles of the thiophene rings ofα-terthienyl.4 Thedistance between the facing intramolecular thiophene rings 2 and 2' is 3.607 ,which is somewhat larger than the distance between the two aromatic rings inoctamethyltetrasila[2.2]paracyclophane (3.4 ).5 These thiophene rings 2 and 2' arelying almost 'face-to-face' whereas in the other thiophene rings, 1 and 3, the Satoms lie above the middle of the opposite rings, resulting in a short S···S distance(3.55 ). These intramolecular S···S distances are slightly smaller than twice the vander Waals radius of sulphur (1.85 ), wheras the other intra- and intermolecularS···S distances are all longer than the van der Waals contacts. The C—S bond

Appendix 2

139

lengths, which range from 1.723(4) to 1.737(5) with an average value of 1.730 ,are close to the reported mean value of 1.712 .6 The Si—Si bond length [2.363(2)

] is slightly longer than a normal Si—Si bond (2.34 ). The conformation of theSi—Si bridges is intermediate betweengauche and eclipsed, the torsion angleC9—Si1—Si2'—C20' being 35.2°. The butyl groups have a planar zigzagconformation except for the butyl group formed by C5, C6, C7 and C8.

Table A2.1 Crystallographic details

Formula C56H84S6Si4 Z 1M 1062.02 Dcalcd (g cm-3) 1.183Space group P1 Radiation (λ/ ) 0.70930a/ 10.468(2) µ(MoKα)/cm-1 3.315b/ 11.755(2) Reflections measured 3669c/ 12.862(1) ReflectionsI ≥ 3 (I) 2570α/˚ 106.96(1) F(000) 572β/˚ 93.72(1) R 0.043γ/˚ 97.68(1) Rw 0.048V/ 3 1491.2(6) Crystal size / mm 0.3x0.3x0.25

Table A2.2 Selected bond lengths (Å) with their e.s.d.'s in parentheses

Si1—Si2 2.363(2) S3—C20 1.723(4) C14—C15 1.407(6)

S1—C9 1.734(5) C9—C10 1.359(6) C15—C16 1.360(6)

S1—C12 1.723(4) C10—C11 1.410(6) C16—C17 1.428(5)

S2—C13 1.726(4) C11—C12 1.375(7) C17—C18 1.363(6)

S2—C16 1.734(5) C12—C13 1.449(6) C18—C19 1.422(6)

S3—C17 1.737(5) C13—C14 1.367(7) C19—C20 1.373(7)

Octabutyl[2.2]tetrasilaterthiophenophane

140

Table A2.3 Selected angles and torsion angles (°) with their e.s.d.'s in parentheses

C9—S1—C12 93.5(2) C13—C14—C15 113.3(4)

C13—S2—C16 92.6(2) C14—C15—C16 114.1(4)

C17—S3—C20 93.8(2) S2—C16—C15 109.8(3)

S1—C9—C10 108.4(3) S3—C17—C18 109.4(3)

C9—C10—C11 115.9(4) C17—C18—C19 113.6(4)

C10—C11—C12 111.9(4) C18—C19—C20 113.9(4)

S1—C12—C11 110.3(3) S3—C20—C19 109.3(3)

S2—C13—C14 110.2(3)

C1—C2—C3—C4 -177.6(5) S2—C16—C17—S3 -175.7(3)

C5—C6—C7—C8 63.2(6) S2—C16—C17—C18 0.3(7)

S1—C12—C13—S2 -174.2(3) C15—C16—C17—C18 176.9(5)

S1—C12—C13—C14 6.6(7) C21—C22—C23—C24 179.1(4)

C11—C12—C13—C14 -170.8(5) C25—C26—C27—C28 174.0(4)

Figure A2.2 Projected packing plot of the molecules in the unit cell and its sur-roundings viewed down the c-axis.

A2.2 EXPERIMENTALThe title compound was synthesized by reacting dichlorotetrabutyldisilane with the

dilithiumsalt of α-terthiophene in diethyl ether. After removal of the polymer byprecipitation followed by chromatographic separation, compound (I) was recrystallizedslowly from a mixture of dichloromethane and methanol.

X-RAY DIFFRACTION

Appendix 2

141

1. Wildeman, J.; Herrema J.K.; Hadziioannou, G.; Schomaker, E.J. Inorg. Organomet.Polym.1991, 1, 567.

2. Gleiter, R.; Schäfer, W.; Krennrich, G.; Sakurai, H.J. Am. Chem. Soc.1988, 110, 4117.3. Herrema J.K.; Wildeman, J.; Wieringa, R.H.; Malliaras, G.G.; Lampoura, S.S.; Hadziio-

annou, G.Polym. Preprints1993, 34, 282.4. Bolhuis, F. van; Wijnberg, H.; Havinga, E.E.; Meijer, E.W.; Staring, G.J.Synth. Met.

1989, 30, 381.5. Sakurai, H.; Hoshi, S.; Kamiya, A.; Hosomi, A.; Kabuto, C.Chem. Lett.1986, 1781.6. Allen, F.H.; Kennard, O.; Watson, D.G.; Brammer, L.; Orpen, A.G.; Taylor, R.J. Chem.

Soc. Perkin Trans. 2, 1987, S1.7. Fair, C.K.MolEN. An Interactive Intelligent System for Crystal Structure Solution, 1990,

Enraf-Nonius, Delft, The Netherlands.8. Nes, G.J.H. van; Bolhuis, F. vanJ. Appl. Cryst.1978, 11, 206.

Data Collection, cell refinement, data reduction, structure solution and structurerefinement:MolEN.7 The X-ray crystal structure analyses were performed at 293 K usingMoKα radiation on a Nonius CAD4F-diffractometer equipped with a graphitemonochromator and interfaced to a VAX-730, using theθ-2θ technique.8 The structure wassolved by direct methods. The remaining H-atoms could be revealed from a Fourierdifference synthesis based on all the non H-atoms. Block-diagonal least-squares ofF withunit weights converged to the finalR and Rw values (Table A2.1), using anisotropictemperature factors for the non H-atoms. In the final refinement the H-atoms wereconstrained to their corresponding C-atoms at a distance of 0.96 .

A2.3 REFERENCES

4,4'-Dioctyl-2,2'-bithiopheneJan K. Herrema, Jurjen Wildeman, Auke Meetsma and Georges HadziioannouActa Crystallographica, 1996, C, to be submitted.

Crystal structureof

4,4'-dioctyl-2,2'-bithiophene

ABSTRACT

The structure of 4,4'-dioctyl-2,2'-bithiophene, C24H38S2, has beendetermined. The molecule is centrosymmetric and has an almostplanar bithiophene skeleton. The bithiophene rings have a transoidarrangement. The octyl side-chains have a planar zigzagconformation and are fully extended.

4,4'-Dioctyl-2,2'-bithiophene

144

A

Figure A3.1 PLUTO drawing illustrating the configuration and the atom-numbering scheme

A3.1 COMMENT

s part of our studies of the influence of substituents on the luminescencespectra of (co)polymers we recently reported the absorption and fluorescence

spectra together with quantum chemical calculations of a series of octyl-substitutedbithiophenes.1 We have studied these low-molecular weight compounds as modelcompounds of the related (co)polymers and are especially interested in their opticaland electronic properties and molecular geometries. Oligomer crystal structures areof interest because of aspects like molecular planarity, molecular packing and therole of the substituent. Furthermore, the bond lengths and angles and torsion anglescan be used to verify quantum-chemical geometry optimizations made in theoreticalstudies of the electronic and structure-related properties of poly(alkylthiophene)s.

The crystal structure of the title compound consists of dimer molecules with acrystallographically imposed centre of inversion. The basic structure consists of twothiophene rings having the S atomstrans to each other. The bithiophene molecule iscoplanar in the solid state. The deviation from the plane is at most 0.009 . TheC—S distances are not significantly different and are slightly longer than thereported mean value of 1.712 .2 The alternating C—C bond lengths of thebithiophene (1.358-1.421-1.365-1.447-1.365-1.421-1.358) clearly indicateconjugation. The thiophene rings exhibit slight distortions from C2v symmetry. Thetwo C—C—C angles differ slightly (3.7°) as do the two S—C—C angles (2.3°).The geometrical features of the title compound are very similar to those of theexternal rings in 4,4',3'',4'''-tetramethylquaterthiophene.3 The octyl groups have a

Appendix 3

145

Figure A3.2 Projected packing plot of the molecules in the unit cell viewed down the b-axis

nearly trans-planar conformation and are not in the plane of the bithiopheneskeleton, the torsion angle around the C3—C5 bond being 70°. The unit cell vieweddown theb-axis, displaying the packing mode, is shown in Figure A3.2. Alonga,layers of the bithiophene skeleton are separated by the octyl chains. The moleculesare arranged in parallel layers along the shortb-axis of 4.94 (see Figure A3.3).Crystal packing is probably largely determined by the hydrophobic interactions ofthe octyl groups.

Table A3.1 Crystallographic details

Formula (C12H19S)2 Z 2M 390.70 Dcalc/ g.cm-3 1.150

Space group P21/c Radiation (λ/ ) 0.70930

a/ 16.490(1) µ(MoKα)/cm-1 2.31

b/ 4.945(1) Reflections measured 2330

c/ 14.805(1) ReflectionsI ≥ 2.5 (I) 1992

α/˚ 90.00 F(000) 428

β/˚ 110.806(5) R 0.033

γ/˚ 90.00 Rw 0.038

V/ 3 1128.5(3) Crystal size/ mm 0.1x0.2x0.5

4,4'-Dioctyl-2,2'-bithiophene

146

Figure A3.3 Projected packing plot of the molecules viewed down the c-axis.

Table A3.2 Selected bond lengths ( ), angles and torsion angles (˚)S1—C1 1.7337(15) C5—C6 1.536(2)

S1—C4 1.7217(16) C6—C7 1.520(2)

C1—C2 1.365(2) C7—C8 1.527(2)

C1—C1' 1.447(2) C8—C9 1.522(2)

C2—C3 1.421(2) C9—C10 1.527(2)

C3—C4 1.358(2) C10—C11 1.519(2)

C3—C5 1.505(2) C11—C12 1.522(2)

C1—S1—C4 91.68(7) S1—C4 —C3 112.43(11)

S1—C1—C2 110.17(11) C3—C5 —C6 112.40(13)

S1—C1—C1' 120.51(11) C5—C6 —C7 113.41(14)

C2—C1—C1' 129.32(14) C6—C7 —C8 113.15(13)

C1—C2—C3 114.24(13) C7—C8 —C9 113.56(14)

C2—C3—C4 111.48(13) C8—C9 —C10 113.66(13)

C2—C3—C5 122.79(13) C9—C10—C11 113.72(13)

C4—C3—C5 125.69(13) C10—C11—C12 112.70(13)

A3.2 ExperimentalThe compound has been obtained from the homo-coupling of the Grignard derivative of

2-bromo-4-octyl-thiophene in diethyl ether using NiCl2(dppp) as catalyst.

X-ray diffractionThe transparent, colourless, block shaped crystal, of approximate size 0.10 x 0.20 x 0.50

mm, used for characterization and data collection was glued on top of a glass fibre andtransferred into the cold nitrogen stream of the low-temperature unit4 mounted on anEnraf-Nonius CAD-4F diffractometer interfaced to a MicroVAX-2000 computer. Preciselattice parameters and orientation matrix were determined from a least-squares treatment ofthe SET45 setting angles of 22 reflections with 14.52 <θ < 17.36. The unit cell wasidentified as monoclinic, the space group was determined to beP21/c. The space group wasderived from the extinct reflections. Reduced cell calculations did not indicate any highermetric lattice symmetry6 and examination of the final atomic coordinates of the structure did

Appendix 3

147

1. Hutten, P.F. van; Gill, R.E.; Herrema, J.K.; Hadziioannou, G.J. Chem. Phys.1994, 99,3218.

2. Allen, F.H.; Kennard, O.; Watson, D.G.; Brammer, L.; Orpen, A.G.; Taylor, R.J. Chem.Soc. Perkin Trans. 2, 1987, S1.

3. Barbarella, G.; Zambianchi, M.; Bongini, A.; Antolini, L.Adv. Mater.1992, 4, 282.4. Bolhuis, F. vanJ. Appl. Cryst.1971, 4, 263.5. Boer, J.L. de; Duisenberg, A.J.M.Acta. Cryst.1984, A40, C410.6. Spek, A.L.J. Appl. Cryst.1988. 21, 578.7. (a) Le Page, Y.J. Appl. Cryst.1987, 20, 264. (b) Le Page, Y.J. Appl. Cryst.1988, 21,

983.8. McCandlish, L.E.; Stout, G.H.; Andrews, L.C.Acta Cryst.1975, A31, 245.

not yield extra metric symmetry elements.7 The intensities of three representative reflectionswhich were measured after every three hours of X-ray exposure time remained constantthroughout data collection indicating crystal and electronic stability. A 360ψ-scan for areflection close to axial (111) showed a variation in intensity of less than 5% about themean value. Intensity data were corrected for scale variation, Lorentz and polarizationeffects, but not for absorption. Standard deviations (I) in the intensities were increasedaccording to analysis of the excess variance of the reference reflection: Variance wascalculated based on counting statistics and the term (P2I2) where P (= 0.022) is theinstability constant8 as derived from the excess variance in the reference reflections.Equivalent reflections were averaged and stated observed if satisfying theI ≥ 2.5 (I)criterion of observability.The structure was solved byDIRDIF,9 employing automated vector-search rotation functions(ORIENT), followed by reciprocal space translation functions (TRACOR) with thethiophene skeleton taken as a starting fragment: all non-hydrogen positions could be located.The positional and anisotropic thermal displacement parameters for the non-hydrogen atomswere refined with block-diagonal least-squares procedures (CRYLSQ)10 minimizing thefunction Q =∑h[w( FO - k FC )2], where the weightw is defined as 1/2(F) and FO and FC

are the observed and calculated structure factor amplitudes, respectively. Refinementfollowed by difference Fourier synthesis resulted in the location of all the hydrogen atompositions, which were included in subsequent refinement. Final refinement onFO byfull-matrix least-squares techniques with anisotropic thermal displacement parameters for thenon-hydrogen atoms and isotropic thermal displacement parameters for the hydrogen atomsconverged atRF = 0.033 (wR = 0.038). A final difference Fourier map did not show residualpeaks outside the range±0.36 e/Å3. Crystal data and experimental details of the structuredetermination are compiled in Table A3.1. Molecular geometry data are collected in TableA3.2. Tables of hydrogen atom positions, thermal displacement parameters, comprehensivelists of bond distances and angles and tables of(FO), (FC) and (F) are available assupplementary material* for this paper. Neutral atom scattering factors were taken fromCromer and Mann.11 Anomalous dispersion factors taken from Cromer and Liberman12 wereincluded in FC. All calculations were carried out on the HP9000/735 computer at theUniversity of Groningen with the program packagesXtal,13 PLATON14 (calculation ofgeometric data) and a locally modified version of the programPLUTO15 (preparation ofillustrations).

A3.3 REFERENCES

4,4'-Dioctyl-2,2'-bithiophene

148

9. Beurskens, P.T.; Admiraal, G.; Beurskens, G.; Bosman, W.P.; García-Granda, S.; Gould,R.O.; Smits, J.M.M.; Smykalla, C.The DIRDIF program system, Technical Report ofthe Crystallography Laboratory, University of Nijmegen, The Netherlands, 1993.

10. Olthof-Hazekamp, R."CRYLSQ", Xtal3.2 Reference Manual.Eds. Hall, S.R.; Flack,H.D.; Stewart, J.M., Universities of Western Australia, Geneva and Maryland. Lamb:Perth, 1992.

11. Cromer, D.T.; Mann, J.B.Acta Cryst.1968, A24, 321.12. Cromer, D.T.; Liberman, D.J. Chem. Phys.1970, 53, 1891.13. Hall, S.R.; Flack, H.D.; Stewart, J.M. Editors.Xtal3.2 Reference Manual. Universities of

Western Australia, Geneva and Maryland, Lamb: Perth, 1992.14. Spek, A.L.Acta Cryst.1990, A46, C-34.15. Meetsma, A.Extended version of the program PLUTO.Univ. of Groningen, The

Netherlands, 1992, (unpublished). Motherwell, W.D.S.; Clegg, W.PLUTO. Program forplotting molecular and crystal structures. Univ. of Cambridge, England (unpublished).

5,5'-Bis(dimethylsilanol)-2,2'-bithiopheneJan K. Herrema, Jurjen Wildeman, Auke Meetsma and Georges HadziioannouActa Crystallographica 1990, C, to be submitted.

Crystal structureof

5,5'-bis(dimethylsilanol)-2,2'-bithiophene

ABSTRACT

We report on the crystal structure of 5,5'-bis(dimethylsilanol)-2,2'-bithiophene. Two crystallographically independent molecules of the titlecompound are present in the asymmetric unit with no atom setting at specialposition. The basic structure consist of two thiophene rings coupled by aC—C bond (1.452(12) and 1.448(12) Å, respectively for the two molecules).The bithiophene skeleton is not coplanar. The dihedral angle between theindividual thiophene rings is 25.7° and 29.2°, respectively. The moleculesare linked into a two-dimensional network by tetrameric intermolecular–OH···O hydrogen bonds.

5,5'-Bis(dimethylsilanol)-2,2'-bithiophene

150

D

Figure A4.1Projected packing plot of the moleculesin the unit cell viewed down the b-axis.

A4.1 COMMENT

ue to difficulties in crystallization, only a limited number of crystallographicstudies1 on oligothiophenes have been published so far. The crystal structure of

the shortest oligothiophene, bithiophene, has been recently reinvestigated2 becausethe first report on the structure by Visser and coworkers3 in 1968 was of lowaccuracy due to crystal decomposition. Most of the X-ray studies of substitutedbithiophenes have been reported in the last decade. Crystal structures of thefollowing compounds have all shown a trans coplanar bithiophene skeleton: 5,5'-dibromo-2,2'-bithiophene,4 5,5'-dimethyl- and 5,5'-bis(trimethylsilyl)-2,2'-bithiophene,5 3,3'-dimethoxy-2,2'-bithiophene,6 4,4'-dimethoxy-2,2'-bithiophene,7

3,3'- and 4,4'-bipentoxy-2,2'-bithiophene,8. This planar skeleton contrasts with thegeneral view of the behaviour of these molecules in solution. There is oneexception: the structure of 2,2'-bithiophene-5-carbaldehyde shows a predominantlycisoid but coplanar conformation.

We present here another exception, the X-ray molecular structure of 5,5'-bis(dimethylsilanol)-2,2'-bithiophene which has a nonplanar bithiophene skeleton.The orthorhombic unit cell contains eight molecules in two sets of discretemolecules (Figure A4.1). The two molecules have a dihedral angle between theconnected thiophene rings of 25.7° and 29.2°, respectively, having the S atomstrans to each other. A view of both discrete molecules and their atomic numbering

Appendix 4

151

scheme is shown in Figure A4.2. Crystal data and experimental details of thestructure determination are compiled in Table A4.1. Molecular geometry data arecollected in Table A4.2.

Typical for main group organometallic hydroxo compounds is the extensivehydrogen bonding. The intermolecular hydrogen bonds of 5,5'-bis(dimethylsilanol)-2,2'-bithiophene form cyclic tetramers in which the hydrogen-bonding motif isR4

4(8)9 like for Ph3SiOH10 and Ph3GeOH.11 Within the cyclic tetramer each oxygenatom forms a hydrogen bond through its acidic proton towards a neighbouringmolecule, and at the same time also forms a hydrogen bond towards an acidicproton of a third molecule. Because each molecule has two sites for hydrogenbonding the molecules are linked in a two-dimensional network in the (a,c) plane.The specifics of the geometry of the intermolecular hydrogen bonds are tabulated inTable A4.3. The O–H···O bond configuration is close to linear. The coordinationaround the silicon is tetrahedral. The average Si—O distance of 1.64(1) agreeswell with the lenghts in Ph3SiOH10 (1.645(7) ) and Ph2Si(OH)212 (1.633(5) ). Thethiophene rings exhibit only slight distorsions from C2v symmetry and are almostplanar. The deviation from their average planes is at most 0.02(1) . The C—S andC—C bond lengths are in good agreement with those reported for otherbithiophenes.

Table A4.1. Crystallographic details

Formula C12H18O2S2Si2 Z 8

M 314.57 Dcalc / g.cm-3 1.291

Space group Pca21 Crystal system orthorhombic

a/ 28.531(4) µ(MoKα) / cm-1 4.53

b/ 6.465(1) Reflections measured 3266

c/ 17.553(2) ReflectionsI ≥ 2.5 (I) 2660

α/˚ 90.00 F(000) 1328

β/˚ 90.00 R 0.046

γ/˚ 90.00 Rw 0.050

V/ 3 3237.7(8) Crystal size / mm 0.1x0.1x0.5

5,5'-Bis(dimethylsilanol)-2,2'-bithiophene

152

Figure A4.2 PLUTO drawing illustrating the configuration and the atom-numberingscheme of both residues.

Table A4.2 Selected geometric parameters

Residue 1 Residue 2

Interatomic Distances ( )

S1—C1 1.753(8) S3—C13 1.732(9)

S1—C4 1.716(8) S3—C16 1.735(9)

S2—C5 1.723(9) S4—C17 1.748(8)

S2—C8 1.723(9) S4—C20 1.738(8)

Si1—O1 1.652(6) Si3—O3 1.640(7)

Si1—C1 1.862(7) Si3—C13 1.878(9)

Si1—C9 1.851(9) Si3—C21 1.839(9)

Si1—C10 1.861(9) Si3—C22 1.844(9)

Si2—O2 1.632(7) Si4—O4 1.645(6)

Si2—C8 1.868(9) Si4—C20 1.855(8)

Si2—C11 1.842(12) Si4—C23 1.858(9)

Si2—C12 1.840(11) Si4—C24 1.847(9)

C1—C2 1.361(11) C13—C14 1.346(12

C2—C3 1.425(12) C14—C15 1.424(12)

C3—C4 1.374(12) C15—C16 1.352(12)

C4—C5 1.452(11) C16—C17 1.448(12

C5—C6 1.336(13) C17—C18 1.354(12)

C6—C7 1.437(12) C18—C19 1.423(12)

C7—C8 1.371(12) C19—C20 1.410(12)

Appendix 4

153

Bond angles (°)C1—S1—C4 92.6(3) C13—S3—C16 92.7(4)

C5—S2—C8 93.2(4) C17—S4—C20 93.2(4)O1—Si1—C1 107.1(3) O3—Si3—C13 108.7(3)O1—Si1—C9 111.8(4) O3—Si3—C21 106.5(4)O1—Si1—C10 108.1(4) O3—Si3—C22 111.1(4)C1—Si1—C9 106.4(4) C13—Si3—C21 110.5(4)C1—Si1—C10 111.7(4) C13—Si3—C22 107.5(4)C9—Si1—C10 111.8(4) C21—Si3—C22 112.5(4)O2—Si2—C8 106.6(3) O4—Si4—C20 107.3(3)O2—Si2—C11 107.6(4) O4—Si4—C23 107.6(3)O2—Si2—C12 111.9(4) O4—Si4—C24 110.6(4)C8—Si2—C11 111.1(4) C20—Si4—C23 113.0(4)C8—Si2—C12 109.5(4) C20—Si4—C24 106.5(4)C11—Si2—C12 110.1(5) C23—Si4—C24 111.9(4)S1—C1—Si1 120.6(4) S3—C13—Si3 122.5(5)S1—C1— C2 109.9(5) S3—C13—C14 109.3(7)Si1— C1— C2 129.5(6) Si3—C13—C14 128.2(7)C1—C2—C3 113.7(8) C13—C14—C15 115.1(8)C2—C3—C4 113.0(8) C14—C15—C16 112.2(8)S1—C4—C3 110.8(6) S3—C16—C15 110.6(7)S1—C4—C5 121.1(6) S3—C16—C17 120.9(6)C3—C4—C5 128.1(8) C15—C16—C17 128.4(8)S2—C5—C4 120.1(6) S4—C17—C16 119.1(6)S2—C5—C6 110.2(7) S4—C17—C18 110.6(6)C4—C5—C6 129.7(8) C16—C17—C18 130.3(8)C5—C6—C7 114.4(8) C17—C18—C19 114.0(8)C6—C7—C8 112.0(8) C18—C19—C20 113.3(7)S2—C8—Si2 121.5(5) S4—C20—Si4 123.1(5)

S2—C8—C7 110.1(7) S4—C20—C19 108.9(6)

Torsion angles (°)O1—Si1—C1—S1 40.7(5) O3—Si3—C13—S3 -45.4(6)

O1—Si1—C1—C2 -136.3(7) O3—Si3—C13—C14 136.6(8)O2—Si2—C8—S2 149.0(5) O4—Si4—C20—S4 -40.1(6)O2—Si2—C8—C7 -33.7(9) O4—Si4—C20—C19 135.8(7)S1—C4—C5—S2 -149.9(5) S3—C16—C17—S4 153.2(5)S1—C4—C5—C6 28.2(13) S3—C16—C17—C18 -25.9(13)C3—C4—C5—S2 28.2(12) C15—C16—C17—S4 -23.9(13)

C3—C4—C5—C6 -153.7(10) C15—C16—C17—C18 156.9(10)

5,5'-Bis(dimethylsilanol)-2,2'-bithiophene

154

Figure A4.3

Table A4.3 Hydrogen-bond geometry with e.s.d. in parentheses.

D—H···A D···A(Å) D—H(Å) H···A(Å) D—H···A(°)

O(1)-H(31)...O(3)i 2.776(8) 0.84(6) 1.94(6) 179(7)

O(2)-H(32)...O(1)ii 2.711(8) 0.83(4) 1.89(4) 171(7)

O(3)-H(33)...O(4)iii 2.758(8) 0.72(9) 2.05(9) 170(10)

O(4)-H(34)...O(2)iv 2.715(8) 0.84(8) 1.88(7) 176(8)

Symmetry codes: (i) -1/2+x,1-y,z; (ii ) -x,1-y,1/2+z; (iii ) 1/2-x,y,-1/2+z; (iv) x,y,z

A4.2 EXPERIMENTAL

X-ray diffractionThe crystal of approximate dimensions 0.10 x 0.15 x 0.51 mm, used for characterization

and data collection, was glued on top of a glass fiber and was transferred to the goniostatand cooled to 130 K by using an on-line liquid- nitrogen cooling system13 mounted on anEnraf-Nonius CAD-4F diffractometer interfaced to a MicroVAX-2000 computer. Unit cellparameters and orientation matrix were determined from a least-squares treatment of theSET414 setting angles of 22 reflections in the range 13.01° < θ < 18.00° . The space groupwas derived from the extinct reflections. The unit cell was identified as orthorhombic, spacegroup Pca21 : the E-statistics showed unambiguous an non-centrosymmetric space group.15

This assignment was confirmed by the solution and the successful refinement in this spacegroup. Reduced cell calculations did not indicate any higher metric lattice symmetry16 andexamination of the final atomic coordinates of the structure did not yield extra metricsymmetry elements.17 The intensities of three representative reflections which were measuredafter every three hours of X-ray exposure time remained constant throughout data collectionindicating crystal and electronic stability. A 360° ψ-scan for a reflection close to axial (101)

Appendix 4

155

1. For a recient review see: Hotta, S.; Waragai, K.Adv. Mater.1993, 5, 896.2. (a) Chaloner, P.A.; Gunatunga, S.R.; Hitchcock, P.B.Acta Cryst.1994, C50, 1941. (b)

Pelletier, M.; Brisse, F.Acta Cryst.1994, C50, 1942.3. Visser, G.J.; Heeres, G.J.; Wolters, J.; Vos A.Acta Cryst.1968, B24, 467.4. Pyrka, G.; Fernando, Q.; Inoue, M.B.; Inoue, M.; Velazquez, E.F.Acta Cryst. 1989,

C44, 562.5. Alemán, C.; Brillas, E.; Davies, A.G.; Fajarí, L.; Giró, D.; Juliá, L.; Pérez, J.J.; Rius, J.

J. Org. Chem.1993, 58, 3091.6. Paulus, E.F.; Dammel, G.; Kämpf, G.; Wegner, P.; Siam, K.; Wolinski, K.; Schäfer, L.

Acta Cryst.1988, B44, 509.7. Paulus, E.F.; Siam, K.; Wolinski, K.; Schäfer, L.J. Mol. Struct.1989, 196, 171.8. Meille, S.V.; Farina, A.; Bezziccheri, F.; Gallazi, M.C.Adv. Mater.1994, 6, 848.9. Etter, M.C.; McDonald, J.C.; Bernstein, J.Acta Cryst.1990, B46, 256.

showed a variation in intensity of less than 13% about the mean value. Intensity data werecorrected for scale variation, Lorentz and polarization effects, but not for absorption.Variance 2(I) was calculated based on counting statistics and the term (P2I2) where P (=0.0168) is the instability constant18 as derived from the excess variance in the referencereflections. Equivalent reflections were averaged and stated observed if satisfying theI ≥ 2.5(I) criterion of observability. The structure was solved by Patterson methods and extension

of the model was accomplished by direct methods applied to difference structure factorsusing the programDIRDIF.19 The positional and anisotropic thermal displacementparameters for the non-hydrogen atoms were refined with block-diagonal least-squaresprocedures (CRYLSQ)20 minimizing the function Q =∑h[w( FO - k FC )2], where theweight w is defined as 1/σ2(F) and FO and FC are the observed and calculated structurefactor amplitudes, respectively. A subsequent difference Fourier synthesis resulted in thelocation of all the hydrogen atoms. Following the inclusion of the positional parameters ofhydrogen atoms in the refinement did not show a well-behaviour for all. Subsequentdifference Fourier maps suggested some degree of rotational disorder for most of the methylgroups. So finally the H31, H32 and H7 were restrained and the methyl-hydrogen atomsbonded to C9, C10, C22, C23 and C24 were placed on ideal positions, in which the found Hatoms served to determine the conformation these hydrogen atoms. The positions werecalculated by using sp-hybridization at the C-atom as appropriate and a fixed C-H distanceof 0.96 Å and they were included in the final refinement riding on their carrier atoms.Refinement on F by full-matrix least-squares techniques with anisotropic thermaldisplacement parameters for the non-hydrogen atoms and one common isotropic thermaldisplacement parameter (U = 0.031(4) Å2 ) for the hydrogen atoms converged atRF = 0.050(wR = 0.046). The polarity of the structure was tested by refinement with i∆F" and -i∆F"values, respectively, giving only marginally differentR values, probably due to twinning inthis respect. A final difference map did not show any significant residual features. Neutralatom scattering factors were taken from Cromer and Mann.21 Anomalous dispersion factorstaken from Cromer and Liberman22 were included inFC. All calculations were carried out onthe HP9000/735 computer at the University of Groningen with the program packagesXtal,23

PLATON24 (calculation of geometric data) and a locally modified version of the programPLUTO25 (preparation of illustrations).

A4.3 REFERENCES

5,5'-Bis(dimethylsilanol)-2,2'-bithiophene

156

10. Puff, H.; Braun, K.; Reuter, H.J. Organomet. Chem.1991, 409, 119.11. Ferguson, G.; Gallagher, J.F.; Murphy, D.; Spalding, T.R., Glidewel, C.; Holden, H.D.

Acta Cryst.1992, C48, 1228.12. Fawcett, J.K.; Camerman, N.; Camerman A.Can. J. Chem.1977, 55, 3632.13. Bolhuis, F. vanJ. Appl. Cryst.1971, 4, 263.14. Boer, J. L. de; Duisenberg, A. J. M.Acta. Cryst.1984, A40, C410.15. Snow, M.R.; Tiekink, E.R.T.Acta Cryst.1988, B44, 676.16. Spek, A.L.J. Appl. Cryst.1988. 21, 578.17. (a) Le Page, Y.J. Appl. Cryst.1987, 20, 264. (b) Le Page, Y.J. Appl. Cryst.1988, 21,

983.18. McCandlish, L.E.; Stout, G.H.; Andrews, L.C.Acta Cryst.1975, A31, 245.19. Beurskens, P.T.; Admiraal, G.; Beurskens, G.; Bosman, W.P.; García-Granda, S.; Gould,

R.O.; Smits, J.M.M.; Smykalla, C.The DIRDIF program system, Technical Report ofthe Crystallography Laboratory, University of Nijmegen, The Netherlands, 1993.

20. Olthof-Hazekamp, R."CRYLSQ", Xtal3.2 Reference Manual.Eds. Hall, S.R.; Flack,H.D.; Stewart, J.M. Universities of Western Australia, Geneva and Maryland. Lamb:Perth, 1992.

21. Cromer, D.T.; Mann, J.B.Acta Cryst.1968, A24, 321.22. Cromer, D.T.; Liberman, D.J. Chem. Phys.1970, 53, 1891.23. Hall, S.R.; Flack, H.D.; Stewart, J.M. Editors,Xtal3.2 Reference Manual, Universities of

Western Australia, Geneva and Maryland, Lamb: Perth, 1992.24. Spek, A.L.Acta Cryst.1990, A46, C-34.25. Meetsma, A.Extended version of the program PLUTO,University of Groningen, The

Netherlands, 1992, (unpublished). Motherwell, W.D.S.; Clegg, W.PLUTO. Program forplotting molecular and crystal structures, University of Cambridge, England (unpublis-hed).