Phosphorus Copies of PPV: π-Conjugated Polymers and Molecules Composed of Alternating Phenylene and Phosphaalkene Moieties
作者:Vincent A. Wright、Brian O. Patrick、Celine Schneider、Derek P. Gates
DOI:10.1021/ja060816l
日期:2006.7.1
A new class of pi-conjugated macromolecule, poly(p-phenylenephosphaalkene) (PPP), is reported. PPPs are phosphorus analogues of the important electronic material poly(p-phenylenevinylene) (PPV) where PdC rather than CdC bonds space phenylene moieties. Specifically, PPPs [sC(6)R(4)-P=C(OSiMe3)sC(6)R'(4)s C(OSiMe3)=P-](n) (1: R = H, R = Me; 11: R = Me, R' = H) were synthesized by utilizing the Becker reaction of a bifunctional silylphosphine, 1,4-C6R4[P(SiMe3)(2)](2), and diacid chloride 1,4-C6R4[COCl](2). Several model compounds for PPP are reported. Namely, mono(phosphaalkene)s RsPdC(OSiMe3)s R' (4: R= Ph, R' = Mes; 7: R = Mes, R' = Ph), C-centered bis(phosphaalkene)s RsPdC(OSiMe3)-C6R'(4)-C(OSiMe3) dPsR (5: R = Ph, R' = Me; 8: R = Mes, R' = H), and P-centered bis(phosphaalkene)s R-C( OSiMe3) dPsC(6)R'4-P=C(OSiMe3) sR (6: R = Mes, R' = H; 10: R = Ph, R = Me). Remarkably, selective Z-isomer formation (i.e., trans arylene moieties) is observed for PPPs when bulky P-substituents are employed while E/Z-mixtures are otherwise obtained. X-ray crystal structures of Z-7, Z, Z-8, and Z, Z-10 suggest moderate pi-conjugation. The twist angles between the PdC plane and unsubstituted arenes are 16 degrees-26 degrees, while those between the PdC plane and methyl-substituted arenes are 59-67. The colored PPPs and their model compounds were studied by UV/vis spectroscopy, and the results are consistent with extended pi-conjugation. Specifically, weakly emissive polymer E/Z-1 (lambda(max)) 338 nm) shows a red shift in its absorbance from model E/Z-4 (lambda(max)) 310 nm), while a much larger red shift is observed for Z-11 (lambda(max) = 394 nm) over Z-7 (lambda(max) = 324 nm).