Three copper(II) complexes of thiophene-2,5-dicarboxylic acid with dissimilar ligands: Synthesis, IR and UV–Vis spectra, thermal properties and structural characterizations

Combined EXAFS and DFT Structure Calculations Provide Structural Insights into the 1:1 Multi‐Histidine Complexes of CuII, CuI, and ZnII with the Tandem Octarepeats of the Mammalian Prion Protein

“…Stepwise coordination of imidazole to Cu 2 + Copper(II) is bound by water molecules in a Jahn-Teller tetragonally distorted octahedral geometry, in which the apical water molecules lie about 0.3 further away from the Cu 2 + centre than those in the four equatorial positions. Such distortion of the apical solvent positions is also observed in some small-molecule crystal structures (e.g., IGUJAW), [34] although recent XAS characterization of dissolved Cu 2 + suggests that the geometry deviates toward an axially elongated square pyramid. [35] Loss of one or more water molecules from the primary coordination sphere of [Cu II (OH 2 ) 6 ] 2 + is unfavourable, with formation of [Cu II (OH 2 ) 5 ] 2 + (creating a vacant coordination site as a precursor for ligand exchange) requiring 7.6 kJ mol À1 , and loss of a second water, forming [Cu II (OH 2 ) 4 ] 2 + , requiring an additional 16.6 kJ mol À1 (Figure 1 A).…”

“…The small-molecule crystal structure IGUJAW displays a square-planar arrangement of four 4-methylimidazole ligands within a Jahn-Teller distorted geometry, with the axial positions occupied by water molecules appearing to be dipole-bound (as opposed to coordinating with the O atom lone pair directed toward the metal centre). [34] The average Cu-Ne bond length from IGUJAW is 2.00 AE 0.02 (the DFT-calculated bond lengths for [Cu II (MeIm) 4 e ] 2 + are 2.023 AE 0.001 ), while the axially bound water molecules in the crystal structure lie at about 2.6 , more consistent with being dipolebound. Using the B3LYP/6-31G(d) method for geometry optimization, Pushie et al have demonstrated a preference for D 2ddistorted geometries away from square planarity for Cu II , [32] similar to the structural distortions reported in other computational studies of Cu II coordination with multiple His donors.…”

“…37 A search of the Cambridge Structure Database38, 39 confirmed the preference of Cu II for square‐planar coordination by tetra‐imidazole‐type complexes and provided a reasonable comparison for the DFT‐calculated [Cu II (MeIm) 4 ε ] 2+ structure. The small‐molecule crystal structure IGUJAW displays a square‐planar arrangement of four 4‐methylimidazole ligands within a Jahn–Teller distorted geometry, with the axial positions occupied by water molecules appearing to be dipole‐bound (as opposed to coordinating with the O atom lone pair directed toward the metal centre) 34. The average Cu‐Nε bond length from IGUJAW is 2.00±0.02 Å (the DFT‐calculated bond lengths for [Cu II (MeIm) 4 ε ] 2+ are 2.023±0.001 Å), while the axially bound water molecules in the crystal structure lie at about 2.6 Å, more consistent with being dipole‐bound.…”

Synthesis, Ab Initio X-ray Powder Diffraction Crystal Structure, and Magnetic Properties of Mn3(OH)2(C6H2O4S)2 Metal–Organic Framework

“…The bridging mode found here is unprecedented for the tdc linker. Supporting Information, Scheme S1 summarizes, to the best of our knowledge, all the coordination modes observed for tdc in MOFs and coordination polymers − ,,,− or complexes, − as well as the new one found in Mn 3 (OH) 2 (C 6 H 2 O 4 S) 2 MOF. The final geometry of tdc obtained here from synchrotron XRPD data (without any constraints) compares very well with that of the optimized molecule (see Supporting Information, Figure S6).…”

Synthesis, Characterization and Investigation of Anticorrosion Properties of an Innovative Metal–Organic Framework, ZnMOF-BTA, on Carbon Steel in HCl Solution

“…The summary of thermal analysis results of ZnMOF-BTA crystals is shown in Table 4. The TGA and DTA results show that ZnMOF-BTA crystals have good crystalline quality and excellent thermal stability [42,43]. In the TGA curve, two major weight losses were observed during the exothermic decomposition process.…”