Electronic Spectra and Photochemistry of Tin(II), Lead(II), Antimony(III), and Bismuth(III) Bromide Complexes in Solution

Abstract

Electronic Spectra, Bromo Complexes, Main Group Metals, PhotochemistryThe electronic spectra of bromo complexes of main group metal ions with an s 2 electronic configuration (SnBr 3~, PbBr 3~, PbBr 4 2~, SbBr 4~, SbBr 6 3 ", BiBr 4~, BiBr 6 3_ ) in acetonitrile show long-wavelength absorption bands which are assigned to metal-centered sp transitions. Compared to the corresponding chloro complexes the sp bands of the bromo complexes appear at longer wavelength due to sp/LMCT mixing (LMCT = ligand-to-metal charge transfer). As a result of this mixing the luminescence which originates from low-energy sp excited states is much weaker than that of the chloro complexes. Moreover, some of the bromo complexes {e.g. BiBr 4 ") undergo a photochemical redox decomposition induced by LMCT excitation.

Photodecomposition of dichloromethane catalyzed by tetrachloroferrate(iii) supported on a Dowex anion exchange resin

“…No decomposition products at all were found after irradiation of a suspension of the CuCl 4 2− /Dowex material in dichloromethane for one hour.…”

“…The photochemical properties of FeCl 4 − are similar to those of FeCl 3 , although FeCl 4 − does not share its Lewis acidity. Photochlorination was the main goal of the work reported by Maldotti et al, who supported FeCl 4 − on Amberlite-900, a polystyrene-based anion exchange resin. 14 The FeCl 4 − ion has higher absorptivity than FeCl 3 in the near UV, 2 and is thus potentially even better suited as a photochemical source of chlorine atoms to initiate chlorination or oxidation processes.…”

“…We have previously reported the homogeneously catalyzed photodegradation of CH 2 Cl 2 in the presence of CuCl 4 2− . 16 The stoichiometry was proposed to be…”

Near-UV photolysis of μ-dibromotetrabromo- dipalladate(II) in chloroform

“…While electron transfer from excited Pd 2 Br 2À 6 to CHCl 3 is possible, and is considered below, it seems most likely that photodissociation is the photochemical pathway for excited Pd 2 Br 2À 6 . As a general rule, excitation into ligand field bands promotes heterolytic dissociation from a metal complex [35], while excitation into ligand-to-metal charge transfer (LMCT) bands promotes homolytic dissociation [36][37][38][39]. Most of the light absorbed by the complex from the broadband illumination is absorbed through strong LMCT bands in the near-UV, while the visible portion of the spectrum comprises lower intensity ligand field bands [26].…”

Photochemical Reductive Elimination of Nitrogen from Triazidogallium(III). Generation of Luminescent Gallium(I)

“…In suitable cases s2 metal ions undergo a further reduction induced by LMCT excitation [9,10,15,16]. If this would apply to GaN3 the primary photochemical step should yield Ga° and azide radicals which decompose to nitrogen atoms and N2 [11,17].…”