Molecular wires comprising pi-extended ethynyl- and butadiynyl-2,5-diphenyl-1,3,4 oxidiazole derivatives: synthesis, redox, structural and optoelectronic properties

Wang, C.; Pålsson, L.-O.; Batsanov, A.S.; Bryce, M.R.

Abstract

2,5-Diphenyl-1,3,4-oxadiazole (OXD) derivatives with terminal ethynyl- (4a,b) and butadiynyl- (8a,b) substituents have been synthesized in high yields. 2-Methyl-3,5-hexadiyn-2-ol has not been exploited previously in the synthesis of terminal butadiynes. Crystals of 8a and 8b are remarkably stable to long-term storage under ambient conditions. The X-ray crystal structure of 8a reveals that the butadiyne moieties are spatially isolated by the aromatic moieties, which explains the high stability. Two series of derived -conjugated molecules, Donor-(CC)n-OXD (n = 1, 2) and OXD-(CC)n-Donor-(CC)n-OXD (n = 1) [Donor = tetrathiafulvalene (TTF), bithiophene, 9-(4,5-dimethyl-1,3-dithiol-2-ylidene)fluorene, and triphenylamine], have been synthesized using Sonogashira reactions and characterized by X-ray crystallography, cyclic voltammetry, and optical absorption/emission spectroscopy. The electron-withdrawing effect of the OXD units is manifested by a positive shift of the donor oxidation waves in these systems: the butadiynylene spacer (n = 2) further shifts the first oxidation waves by 40-80 mV compared to analogues n = 1. The absorption spectra of TTF-OXD hybrids 10d and 11 are blue-shifted by 80 nm compared to the bithienyl-bridged derivative 10f and are similar to the butadiynyl-OXD building-block 8a, demonstrating that conjugation is disrupted by a neutral TTF unit. Solutions of the TTF-OXD and 9-(4,5-dimethyl-1,3-dithiol-2-ylidene)fluorene-OXD hybrids, 10d, 10g, 11, and 13, are only very weakly fluorescent due to quenching from the electron-donor moieties. In contrast, the triphenylamine-OXD hybrids 12a, 12b, 14a, and 14b are fluorescent; the PLQYs of the butadiynylene derivatives 14a and 14b are lower than those of the ethynylene-bridged analogues 12a and 12b.

Citation

Wang, C., Pålsson, L., Batsanov, A., & Bryce, M. (2006). Molecular wires comprising pi-extended ethynyl- and butadiynyl-2,5-diphenyl-1,3,4 oxidiazole derivatives: synthesis, redox, structural and optoelectronic properties. Journal of the American Chemical Society, 128(11), 3789-3799. https://doi.org/10.1021/ja0577600

• Journal Article Type: Article
• Publication Date: Mar 1, 2006
• Deposit Date: Feb 25, 2008
• Journal: Journal of the American Chemical Society
• Print ISSN: 0002-7863
• Electronic ISSN: 1520-5126
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 128
• Issue: 11
• Pages: 3789-3799
• DOI: https://doi.org/10.1021/ja0577600
• Keywords: Light-emitting-diodes, Ray crystal-structures, Negative differential resistance, Electron-transporting materials, 2 tetrathiafulvalene complexes, Charge-transfer complexation, Organic electroluminescent, Conjugation stabilization, Selective synthesis.
• Public URL: https://durham-repository.worktribe.com/output/1555966