4H-Pyran-4-ylidenes: Strong Proaromatic Donors for Organic Nonlinear Optical Chromophores

Abstract

Merocyanines where a polyenic spacer separates a 4H-pyran-4-ylidene moiety and different strong organic acceptors have been synthesized. According to NMR studies and X-ray diffraction data, these compounds have weakly alternated structures and remarkably zwitterionic ground states, with a partial aromatic character that is compared to those of other pyran derivatives. The proaromaticity of the 4H-pyran-4-ylidene donor lies behind the cyanine-like behavior and low (positive or negative) second-order optical nonlinearities of the shorter derivatives. On the other hand, lengthening the pi-spacer gives rise to rapidly increasing mubeta(1907) values up to 17,400 x 10(-48) esu.

Recent advances on push–pull organic dyes as visible light photoinitiators of polymerization

“…C. Pigot et al European Polymer Journal xxx (xxxx) xxx-xxx A5, [130] methyl-containing tricyanofurans A6, [131] substituted tricyanopropenes A7, [132] pyran derivatives A8 and A9, [133,134] 1,1,3-tricyano-2-substituted propenes A10, [135] isoxazolones A11, [136] hydantions and rhodanines A12, [137] pyrazines A13, [138] dicyanoimidazoles A14, [139] [141] dicyanovinyl-thiophen-5-ylidenes A17 [142] and 9-methylene-2,4,5,7-tetranitro-9H-fluorene A18 [143] can be mentioned. Another appealing feature of push-pull dyes is the possibility to design these structures by using a convergent approach.…”

Pyranylidene/thienothiophene-based organic sensitizers for dye-sensitized solar cells

“…γ-Pyranylidene-containing dyes constitute a class of molecules deeply studied in the field of photonics and organic electronics. Its proaromatic character [21] improves the charge transfer process through the gain in aromaticity. The synthetic versatility provided by the building blocks of this type of compounds allowed the synthesis and characterization of a variety of structures, affording materials with interesting properties, like second-order optical activity [22] or two-photon absorption, [23] and OSCs.…”

Recent Advances on Nitrofluorene Derivatives: Versatile Electron Acceptors to Create Dyes Absorbing from the Visible to the Near and Far Infrared Region

“…If the number of groups used as electron donors cannot be calculated anymore in regards to the diversity of structures, the number of electron acceptors that can be covalently linked to electron donors is more limited, as exemplified by the list of molecules 1–17 presented in the Figure 1. Notably, malononitrile 1 [20], indanedione derivatives 2 [21], (thio)barbituric derivatives 3 [22], Meldrum derivatives 4 [23], pyridinium 5 [24], methyl-containing tricyanofurans 6 [25], substituted tricyanopropenes 7 [26], pyran derivatives 8 and 9 [27,28], 1,1,3-tricyano-2-substituted propenes 10 [29], isoxazolones 11 [30], hydantions and rhodanines 12 [31], pyrazines 13 [32], dicyanoimidazoles 14 [33], benzo[ d ]thiazoliums 15 [34], benzo[ d ]imidazoliums 16 [35], and dicyanovinyl-thiophen-5-ylidenes 17 [36] can be cited as the most common acceptors.…”