Photoluminescence properties of tetrahedral zinc(ii) complexes supported by calix[4]arene-based salicylaldiminato ligands. Issue 16 (12th April 2018)

• Record Type: Journal Article
• Authors: Ullmann, Steve; Schnorr, René; Laube, Christian; Abel, Bernd; Kersting, Berthold
• Is Part Of: Dalton transactions. Volume 47:Issue 16(2018)
• Page Start: 5801
• Page End: 5811
• Publication Date: 2018-04-12
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c8dt00757h
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The photophysical properties of zinc salicylaldiminato calix[4]arene complexes can be fine-tuned by the salicylaldiminato substituents and the calix[4]arene conformation. Abstract : The synthesis and photophysical properties of four new hybrid salicylaldiminato-calix[4]arene ligands and their corresponding zinc(ii ) complexes are described. The Schiff bases were obtained from condensation reactions between cone -25, 27-di(aminoethoxy)-26, 28-dihydroxy-calix[4]arene and salicylaldehyde (H2 L 1 ) or o -vanillin (H2 L 2 ) and 1, 3- alt -25, 27-di(aminoethoxy)-26, 28-di( n -propyloxy)-calix[4]arene and 3, 5-di- tert -butyl-salicylaldehyde (H2 L 3 ) or o -vanillin (H2 L 4 ). Complexation reactions were investigated by ESI-MS, IR, NMR, UV-vis absorption and steady-state and time resolved fluorescence spectroscopy, and X-ray crystallography. All ligands support 1 : 1 complexes (ZnL 1 –ZnL 4 ), with equilibrium constants derived from absorption spectrophotometry in the range log K 11 = 5.5–8.2 (MeCN or MeOH/CH2 Cl2, I = 0.01 M). The zinc complexes show blue fluorescence, both in solution as well as in the solid state, with λ em, Φ f, and τ ranging from 472–504 nm, 0.11–0.60, and 2–9 ns, respectively. The nature of the substituents on the salicylaldiminato fragments was found to be the main parameter that influences the photophysical properties of the zinc complexes. Insights into the electronic nature of the UV-vis transitions were obtained with time dependent density functional theory (TD-DFT) calculations.