Iminium Salts of ω-Dithiafulvenylpolyenals: An Easy Entry to the Corresponding Aldehydes and Doubly Proaromatic Nonlinear Optic-phores

Abstract

A short, high-yielding route to omega-dithiafulvenylpolyenals (1) via the corresponding iminium salts (2) and starting from trimethyl-1,3-dithiolium tetrafluoroborate is reported. The Knoevenagel reactions of either 1 or 2 with isoxazolone-containing acceptors afford merocyanines 7 and 9, in a process that is often accompanied by a vinylene-shortening side reaction. Experimental and theoretical studies reveal that compounds 7 and 9, featuring two proaromatic end groups, are strongly polarized and show good second-order nonlinear optical responses.

Decreased Optical Nonlinearities upon CF3 Substitution on Tricyanofuran Acceptors

“…It can be seen ( Table 1) that, for a given acceptor, µ values rapidly increase on lengthening the spacer. Thus, µ 0 for the longest TCF-containing compound (8) is the highest ever reported for a 1,3-dithiole based NLOphore 8,16 and compares favorably to that measured for benchmark chromophore CLD-1 (µ ) 14065 × 10 -48 esu at 1907 nm). 4 Rotamers A are predicted (Table 1) to contribute higher µ 0 values than rotamers B, 13b a fact which is partly due to the higher ground-state and transition dipole moments of the former (see the Supporting Information).…”

Tetrathiafulvalene–Polychlorotriphenylmethyl Dyads: Influence of Bridge and Open‐Shell Characteristics on Linear and Nonlinear Optical Properties

“…Indeed, after the first example reported in 1998 by N. Martín, J. Garín and coworkers, [9] many other TTF-based pushpull derivatives with closed-shell electronic structure exhibiting large NLO responses have been described. [10][11][12][13][14][15][16][17][18] On the other hand, molecular materials with open-shell electronic structures have also aroused the interest of many researchers because of their high potentiality as NLO-phores. [19][20][21][22][23][24] Thus, a few years ago, some of us reported the second-order non-linear optical (SONLO) response of a family of polychlorotriphenylmethyl (PTM) radical derivatives showing large β hyperpolarizability values.…”

“…Regarding the building blocks, the tetrathiafulvalene (TTF) moiety has been widely used as an efficient electron‐donor unit for synthesizing TTF‐π‐A structures with appealing NLO properties. Indeed, after the first example reported in 1998 by N. Martín, J. Garín and co‐workers, many other TTF‐based push–pull derivatives with closed‐shell electronic structures exhibiting large NLO responses have been described . On the other hand, molecular materials with open‐shell electronic structures have also aroused interest because of their high potentiality as NLO‐phores .…”

An Efficient Synthesis of 4-Arylmethylidene-3-substituted-Isoxazol-5(4H)-ones in Aqueous Medium

“…Isoxazolone is a class of heterocyclic compounds having a remarkable number of pharmaceutical applications and have been demonstrated to be versatile building blocks in the synthesis of natural products , in optical recording, and nonlinear optical research . 4‐(Arylmethylene)‐isoxazol‐5‐ones are known to be useful building blocks for the preparation of fused heterocycles .…”