Large First Hyperpolarizabilities in Push-Pull Polyenes by Tuning of the Bond Length Alternation and Aromaticity

Abstract

Conjugated organic compounds with 3-phenyl-5-isoxazolone or N,N ′-diethylthiobarbituric acid acceptors have large first molecular hyperpolarizabilities (β) in comparison with compounds with 4-nitrophenyl acceptors. For example, julolidinyl-(CH=CH) 3 -CH= N,N ′-diethylthiobarbituric acid, which has 12 atoms between the donor and acceptor, has a β(0) of 911 × 10 -30 electrostatic units, whereas (CH 3 ) 2 NC 6 H 4 –(CH=CH) 4 –C 6 H 4 NO 2 , with 16 atoms between its donor and acceptor, has a β(0) of 133 × 10 -30 electrostatic units. The design strategies demonstrated here have resulted in chromophores that when incorporated into poled-polymer electrooptic modulators exhibited significant enhancements in electrooptic coefficients relative to polymers containing the commonly used dye Disperse Red-1. Poled polymer devices based on these or related chromophores may ultimately lead to high-speed electrooptic switching elements with low drive-power requirements, suitable for telecommunications applications.