Pyrazolate-bridged group 11 metal(I) complexes: Substituent effects on the supramolecular structures and physicochemical properties

Polynuclear homoleptic pyrazolate-bridged group 11 metal(I) complexes with three different alkyl substituted pyrazolate anions, 3,5-diisopropylpyrazolate (3,5-iPr2pz− = L1−), 3-tert-butyl-5-isopropylpyrazolate (3-tBu-5-iPrpz− = L3−), and 3,5-di-tert-butylpyrazolate (3,5-tBu2pz− = L4−), i.e. [Cu(μ-3,5-iPr2pz)]3 (CuL1), [Ag(μ-3,5-iPr2pz)]3 (AgL1), [Au(μ-3,5-iPr2pz)]3 (AuL1), [Cu(μ-3-tBu-5-iPrpz)]4 (CuL3), [Ag(μ-3-tBu-5-iPrpz)]3 (AgL3), [Au(μ-3-tBu-5-iPrpz)]4 (AuL3), [Cu(μ-3,5-tBu2pz)]4 (CuL4), [Ag(μ-3,5-tBu2pz)]4 (AgL4), and [Cu(μ-3,5-tBu2pz)]4 (AuL4), were systematically synthesized in order to investigate the influence of pyrazole bulkiness on their structures and physicochemical properties. The structural characterization indicates that the geometries are greatly influenced by the steric hindrance exerted by the substituent groups of the pyrazolyl rings and the differences of the central metal (I) ionic radius (Cu+ < Au+ < Ag+). These complexes were also characterized by spectroscopic techniques, namely, UV–Vis, IR/far-IR, Raman, and luminescence spectroscopy.