Amplified Optical Nonlinearity in a Self-Assembled Double-Strand Conjugated Porphyrin Polymer Ladder
详细信息 查看全文
- 作者：Thomas E. O. Screen ; Jonathan R. G. Thorne ; Robert G. Denning ; David G. Bucknall ; and Harry L. Anderson
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：August 21, 2002
- 年：2002
- 卷：124
- 期：33
- 页码：9712 - 9713
- 全文大小：84K
- 年卷期：v.124,no.33(August 21, 2002)
- ISSN：1520-5126
文摘
Addition of 4,4'-bipyridyl to a solution of a meso-meso butadiyne-linked conjugated zinc porphyrin polymer in chloroform results in self-assembly of a double-strand ladder complex. Excess ligand causes this duplex to dissociate into single strands. These binding processes were elucidated by near-IR and NMR titrations, as well as by gel permeation chromatography and small-angle neutron scattering. Ladder-making and -breaking are highly cooperative, with Hill coefficients of 3.0 and 3.7, respectively. Self-assembly of the ladder holds the 
ges/gifchars/pi.gif" BORDER=0 >-system in a planar conformation, enhancing the conjugation, resulting in a red-shift and intensification of the Q-band. Both the real and imaginary parts of the third-order susceptibility per macrocycle are amplified by ladder formation, as revealed by degenerate four-wave mixing measurements at 1064 nm. At this wavelength, the double-strand polymer complex has ges/entities/verbar.gif">ges/gifchars/chi.gif" BORDER=0 >(3)xyyxges/entities/verbar.gif"> = 6.0 × 10-17 m2 V-2 per macrocycle, compared with 6.6 × 10-18 m2 V-2 for the single-strand polymer under the same conditions.