1,4‐Phenylene and 2,5‐Thienylene π‐Linkers in Charge‐Transfer Chromophores

Abstract

Fifteen model charge-transfer chromophores with ferrocene donors, NO 2 acceptors, and 1,4-phenylene and 2,5-thienylene p-linkers were synthesized and their properties investigated by X-ray analysis, electrochemistry, absorption spectra, and DFT calculations. Structure-property relationships were further evaluated to answer the question of suitability of the p-linkers in the construction of chromophore backbone. Gradual replacement of 1,4-phenylene with 2,5thienylene and p-linker extension resulted in a lower HOMO-LUMO gap, a bathochromic shift of both charge-transfer bands, and overall planarization of the molecule. Hence, thiophene, when incorporated into a chromophore backbone, is a more polarizable moiety that allows very efficient intramolecular charge transfer.

Modulation of (non)linear optical properties in tripodal molecules by variation of the peripheral cyano acceptor moieties and the π-spacer

“…A comparison of chromophores 4 and 11 also allows comparison of 1,4-phenylene and 2,5-thienylene π-systems. 34 With very similar oxidation potentials (1.04 and 1.09 V), the later showed significantly lowered first reduction potential (-1.45 vs. -1.85 V) as well as the electrochemical gap (∆E = 2.89 vs. 2.54 V).…”

“…This is in contrast to general trends observed for second order NLO chromophores. 34 However, an addition of the second cyano group into 11 leads to 12 with more than three-times higher 2PA cross-section without affecting the florescence quantum yield. This makes the thiophene substituted chromophores 11 and 12 extremely sensitive to the number of cyano groups.…”

Alphabet‐Inspired Design of (Hetero)Aromatic Push–Pull Chromophores

“…The electron‐releasing moieties (D) comprise N , N ‐dialkyl(aryl)amines, indole, carbazole, and proaromatic 4 H ‐pyran‐4‐ylidene; the A part is represented by the strongest electron‐withdrawing moieties, such as DCV, (thio)barbituric acid, isoxazolone, and TCF. The π‐system is often extended through polarizable 2,5‐thienylene linkers 40. It turned out that the central pyranylidene moiety behaved strictly as a polyenic spacer, not as an auxiliary donor, unlike the pyranylidene terminal donor.…”

Rückgewinnung anorganischer Wertstoffe mit Bordotierten Diamantelektroden

“…The π‐conjugated spacer plays a determining role in D‐π‐A systems,4 and is the most studied system for second‐order NLO materials, given that the intramolecular charge transfer (ICT) throughout this fragment defines to a large extent the final properties in this type of compound. Olefinic spacers represent, in principle, the most effective way to achieve charge redistribution between D and A groups, but they lead to poor thermal and chemical stability.…”