Tungsten and molybdenum oxo complexes of tetrakis(phenyldiazenyl)calix[4]arene substituted derivatives: EHMO calculations, spectroscopic characterization, and perturbations of the photophysical properties by neutral guest molecules.

TitleTungsten and molybdenum oxo complexes of tetrakis(phenyldiazenyl)calix[4]arene substituted derivatives: EHMO calculations, spectroscopic characterization, and perturbations of the photophysical properties by neutral guest molecules.
Publication TypeJournal Article
Year of Publication1996
AuthorsHarvey, PD, Gagnon, J, Provencher, R, Xu, B, Swager, TM
JournalCanadian Journal of Chemistry
Volume74
Pagination2279–2288
ISSN0008-4042
Keywordsluminescence metal oxo complex phenyldiazenyl calixarene, photophysics metal oxo complex phenyldiazenyl calixarene
Abstract

Bowl-shaped chromophores fabricated with tungsten and molybdenum oxo complexes of calix[4]arenes substituted at the para positions with phenyldiazenyl (R2C6H3N2) derivs. are investigated. The nature of the lowest energy excited states has been addressed theor. using EHMO calcns. and exptl. using UV-visible, luminescence, and polarized emission spectroscopy at 77 K. The lowest energy excited states are intraligand (azobenzene fragment) $π$$π$* (S2 and T2) and n$π$* states (S1 and T1). The compds. are weakly luminescent in the 600-630 nm range exhibiting emissions arising from the 1($π$$π$*) states (S2 → S0, 1 < $\tau$e < 4 ns, and 3 × 10-3). The region located above 900 nm was not investigated. Evidence for guest-host chem. has been demonstrated by 1H-NMR spectroscopy, and the binding consts. for two of the compds. with pyridine in toluene as a solvent were obtained by UV-visible spectroscopy. The presence of a guest mol. inside the luminescent metal oxo complex of a calix[4]arene hosts decreases the emission lifetimes. [on SciFinder(R)]

DOI10.1139/v96-256