Synthesis and Characterization of Cu(II) and Mixed-Valence Cu(I)Cu(II) Clusters Supported by Pyridylamide Ligands

Abstract

A group of copper complexes supported by polydentate pyridylamide ligands H 2 bpda and H 2 ppda were synthesized and characterized. The two Cu(II) dimers [Cu II 2 (Hbpda) 2 (ClO 4 ) 2 ] (1) and [Cu II 2 (ppda) 2 (DMF) 2 ] (2) were constructed by using neutral ligands to react with Cu(II) salts. Although the dimers showed similar structural features, the second-sphere interactions affect the structures differently. With the application of Et 3 N, the tetranuclear cluster (HNEt 3 )-[Cu II 4 (bpda) 2 (μ 3 -OH) 2 (ClO 4 )(DMF) 3 ](ClO 4 ) 2 (3) and hexanuclear cluster (HNEt 3 ) 2 [Cu II 6 (ppda) 6 (H 2 O) 2 (CH 3 OH) 2 ](ClO 4 ) 2 (4) were prepared under similar reaction conditions. The symmetrical and unsymmetrical arrangement of the ligand donors in ligands H 2 bpda and H 2 ppda led to the dramatic conformation difference of the two Cu(II) complexes. As part of our effort to explore mixed-valence copper chemistry, the triple-decker pentanuclear cluster [Cu II 3 Cu I 2 (bpda) 3 (μ 3 -O)] ( 5) was prepared. XPS examination demonstrated the localized mixed-valence properties of complex 5. Magnetic studies of the clusters with EPR evidence showed either weak ferromagnetic or antiferromagnetic interactions among copper centers. Due to the trigonal-planar conformation of the trinuclear Cu(II) motif with the μ 3 -O center, complex 5 exhibits geometric spin frustration and engages in antisymmetric exchange interactions. DFT calculations were also performed to better interpret spectroscopic evidence and understand the electronic structures, especially the mixed-valence nature of complex 5.

Novel Copper-Containing Cytotoxic Agents Based on 2-Thioxoimidazolones

“…Two reversible waves were observed at the E range of 0.3–0.6 mV vs Ag/AgCl, which could be ascribed to the one-electron oxidation of Cu +1 to Cu +2 and chlorine oxidation, respectively . Recently, Schneider et al reported a mixed-valence pyridylamide-based complex, and the oxidation of Cu +2 and Cu +1 centers was irreversible . In our case, both reversible oxidation and reduction are observed.…”

Sustained, photocatalytic CO2 reduction to CH4 in a continuous flow reactor by earth-abundant materials: Reduced titania-Cu2O Z-scheme heterostructures

“…The Cu 2p XPS spectra for RT-Cu0.75 ( Fig. 4b) display two peaks appearing at binding energies of 932 eV and 951.8 eV corresponding to Cu 2p3/2 and Cu 2p1/2 respectively; these binding energies are commonly attributed to the presence of Cu 1+ [42]. The signatory satellite peak for Cu 2+ , which appears in the region of 940-945 eV, is not observed in the XPS spectra [43], a result J o u r n a l P r e -p r o o f in accordance with prior studies wherein this oxidation state is often undetected in XPS analysis despite the presence of Cu 2+ [26,44].…”

Sonochemical synthesis of a trinuclear Cu(ii) complex with open coordination sites for the differentiable optical detection of volatile amines

“…6,7 Generally, a polynuclear complex is held into macromolecules by non-covalent interactions such as hydrogen bonding, hydrophobic, p-p, and electrostatic interactions. [8][9][10] In addition, some Cu(II) multinuclear complexes contain an open coordination site to interact with Lewis basic molecules. 11,12 Interactions between the unsaturated Cu(II) unit and guest molecules usually affect the alteration in the coordination environment of Cu(II) core as well as the molecular packing, leading to chromotropic phenomena.…”