title: Experimental and computational studies of a multi-electron donor-acceptor ligand containing the thiazolo[5,4-d]thiazole core and its incorporation into a metal-organic framework.
abstract: A ligand containing the thiazolo[5,4-d]thiazole (TzTz) core (acceptor) with terminal triarylamine moieties (donors), N,N'-(thiazolo[5,4-d]thiazole-2,5-diylbis(4,1-phenylene))bis(N-(pyridine-4-yl)pyridin-4-amine (1), was designed as a donor-acceptor system for incorporation into electronically active metal-organic frameworks (MOFs). The capacity for the ligand to undergo multiple sequential oxidation and reduction processes was examined using UV/Vis-near-infrared spectroelectrochemistry (UV/Vis-NIR SEC) in combination with DFT calculations. The delocalized nature of the highest occupied molecular orbital (HOMO) was found to inhibit charge-transfer interactions between the terminal triarylamine moieties upon oxidation, whereas radical species localized on the TzTz core were formed upon reduction. Conversion of 1 to diamagnetic 2+ and 4+ species resulted in marked changes in the emission spectra. Incorporation of this highly delocalized multi-electron donor-acceptor ligand into a new two-dimensional MOF, [Zn(NO3 )2 (1)] (2), resulted in an inhibition of the oxidation processes, but retention of the reduction capability of 1. Changes in the electrochemistry of 1 upon integration into 2 are broadly consistent with the geometric and electronic constraints enforced by ligation.
authors.affiliation: School of Chemistry, The University of Sydney, NSW 2006 (Australia), Fax: (+61) 2 9351 3329.
authors.forename: Felix J
authors.initials: FJ
authors.lastname: Rizzuto
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Faust
authors.forename: Bun
authors.initials: B
authors.lastname: Chan
authors.forename: Carol
authors.initials: C
authors.lastname: Hua
authors.forename: Deanna M
authors.initials: DM
authors.lastname: D'Alessandro
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Kepert
keywords: density functional calculations; donor-acceptor systems; electron transfer; metal-organic frameworks; spectroelectrochemistry