Tetrahalidocuprates(ii)—structure and EPR spectroscopy. Part 1: Tetrabromidocuprates(ii)

Abstract

Tetrahalidocuprates(II) show a high degree of structural flexibility. We present the results of crystallographic and electron paramagnetic resonance (EPR) spectroscopic analyses of four new tetrabromidocuprate(II) compounds and compare the results with previously reported data. The cations in the new compounds are the sterically demanding benzyltriphenylphosphonium, methyltriphenylphosphonium, tetraphenylphosphonium, and hexadecyltrimethylammonium ions; they were used to achieve a reasonable separation of the paramagnetic Cu(II) ions for EPR spectroscopy. X-Ray crystallography shows that in all four complexes the [CuBr 4 ] 2À units have a distorted tetrahedral coordination geometry which is in agreement with DFT calculations. The EPR hyperfine structure was not resolved. This is due to the exchange broadening resulting from still incomplete separation of the paramagnetic Cu(II) centres. Nevertheless, the principal values of the electron Zeemann tensor (g || and g > ) of the complexes could be determined. A correlation of structural (X-ray) parameters with the spin density at the copper centres (DFT) is well reflected in the EPR spectra of the bromidocuprates. This enables the correlation of X-ray and EPR parameters to predict the structure of tetrabromidocuprates in physical states other than the crystalline state. As a result, we provide a method to structurally characterize [CuBr 4 ] 2À in, for example, ionic liquids or in solution, which has important implications for e.g. catalysis or materials science.

Quaternary Phosphorus‐Induced Iodocuprate(I)‐Based Hybrids: Water Stabilities, Tunable Luminescence and Photocurrent Responses

“…However, compared with the extensively reported cluster‐based iodocuprates, the polymeric anionic iodocuprates are still underdeveloped due to lack of efficient synthetic strategies, and the commonly used structure directing agents (SDAs) are N/S‐bearing organic cations with different skeleton flexibility, hydrophobicity and electronic structures,, , , for example, methylnicotinohydrazide dication (MNH 2+ ) . The quaternary phosphorus salts were seldom utilized as SDAs in iodocuprate system, and only limited iodocuprates/quaternary phosphorus hybrids were reported …”

The crystal structure ofN-butylpyridinium bis(μ2-dichlorido)-tetrachloridodicopper(II), C18H28N2Cu2Cl6

“…Of particular interest to the current study, metalcontaining ILs (MILs) have been studied for a variety of properties such as their structural flexibility [23,24], electrochemical behavior [25], and the exploitation of their unique redox behavior, for example in applications for mercury removal from natural gas, etc. [26][27][28][29].…”

Ionogels Based on Poly(methyl methacrylate) and Metal-Containing Ionic Liquids: Correlation between Structure and Mechanical and Electrical Properties

“…The solid-state UV/Vis spectra therefore suggest that either there is a confinement effect on the coordination geometry around the metal ion or there is a weak interaction between IL and PMMA centered around the metal ion. Alternatively, there could also be changes in the IL-IL interaction on confinement, similar to cation-induced geometry variations in [CuCl 4 ] 2− and [CuBr 4 ] 2− anions [ 81 , 82 ]. The apparent contradiction between IR (suggesting no interaction between IL and PMMA) and UV/Vis spectroscopy (possibly suggesting a weak interaction) is resolved because IR spectroscopy does not probe the M–Cl bonds whereas UV/Vis does: in essence these data therefore suggest that—if there is an interaction at all—it stems from the IL anion and the PMMA.…”