Synthesis, Structure, and Nonlinear Optical Properties of Diarylpolyynes

Abstract

A series of alpha,omega-diarylpolyynes has been synthesized. In addition to the synthesis of three hexaynes (3a-c), a notably improved synthesis of 1,16-diphenylhexadecaoctayne (5) is described. The third-order nonlinear optical characteristics for these molecules have been studied and show a substantial increase in molecular hyperpolarizability (gamma) as a function of increasing length. The unusual solid-state structures of compounds 3a and 3b are reported.

Crystal structure of 2-[6-(2-formylphenoxy)-2,4-hexadiynyloxy]- benzaldehyde, C20H14O4

“…The p conjugation has attracted synthetic chemists for the construction of conjugated systems by coupling of a,w-polyacetylenes to annulenes [2]. Due to their structural simplicity linear conjugated polyynes have been envisioned as molecular wires [3][4][5][6]. Meanwhile, diacetylene compounds are starting material for the synthesis of heterocyclic compounds.…”

Carbon-atom wires: 1-D systems with tunable properties

“…89 It has been shown that the nature of the endgroups is negligible for longer CAWs in the two series based on UV/vis spectroscopy, 127 and it was thus reasonable to conclude that the origin of the NLO behaviour in both the cases was derived primarily from the sp-hybridized carbon chain. 128 The combined linear and nonlinear optical results from these studies implied that polyynes might function as ideal conjugated systems, 129 which have motivated other studies of the NLO behaviour of sp-carbon containing systems, 130,131 including optical limiting applications. [132][133][134][135][136] According to their structure and bond coordination, CAWs can be expected to show very good mechanical properties.…”

Connection among Raman wavenumbers, bond length alternation and energy gap in polyynes

“…[16 -19] Many theoretical studies [20 -30] analyzed these systems in order to characterize their properties while the development in the chemical synthesis of polyynes has produced new interesting systems for theoretical and experimental investigations. [1,2,8,9,15] In a recent series of papers, we investigated the correspondence between the vibrational properties of carbyne and that of finite molecules (oligoynes) in the frame of the effective conjugation coordinate (ECC) model [31 -35] by using both first-principles calculations [36,37] and semiempirical models. [30,38,39] In particular, long-range interactions have proved to be of fundamental importance both for a correct interpretation of the Raman spectra of oligomers [36] and for a suitable modeling of the phonon dispersion branches of the corresponding polymer.…”