Inorganic Phosphate and Arsenate within New Tetranuclear Copper and Zinc Complexes: Syntheses, Crystal Structures, Magnetic, Electrochemical, and Thermal Studies

Abstract

Three, PO 4 3– /HPO 4 2– and AsO 4 3– -incorporated, new tetranuclear complexes of copper(II) and zinc(II) ions have been synthesized and fully characterized. In methanol–water, reactions of H 3 cpdp (H 3 cpdp = N , N ′-Bis[2-carboxybenzomethyl]- N , N ′-Bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol) with copper(II) chloride in the presence of either NaOH/Na 2 HPO 4 ·2H 2 O or KOH/Na 2 HAsO 4 ·7H 2 O lead to the isolation of the tetranuclear complexes Na 3 [Cu 4 (cpdp) 2 (μ 4 -PO 4 )](OH) 2 ·14H 2 O ( 1 ) and K 2 [Cu 4 (cpdp) 2 (μ 4 -AsO 4 )](OH)·16 2 / 3 H 2 O ( 2 ), respectively. Similarly, the reaction of H 3 cpdp with zinc(II) chloride in the presence of NaOH/Na 2 HPO 4 ·2H 2 O yields a tetranuclear complex, Na(H 3 O) 2 [Zn 4 (cpdp) 2 (μ 4 -HPO 4 )]Cl 3 ·12 1 / 2 H 2 O ( 3 ). All complexes are characterized by single-crystal X-ray diffraction and other analytical techniques, such as Fourier transform infrared and UV−vis spectroscopy, thermogravimetric and electrochemical studies. The solid-state molecular framework of each complex contains two monocationic [M 2 (cpdp)] + (M = Cu, Zn) units, which are exclusively coordinated to either phosphate/hydrogen phosphate or arsenate groups in a unique mode. All three complexes exhibit a μ 4 :η 1 :η 1 :η 1 :η 1 bridging mode of the PO 4 3– /HPO 4 2– /AsO 4 3– groups, with each bridging among four metal ions. The thermal properties of all three complexes have been investigated by thermogravimetric analysis. Low-temperature magnetic studies of complexes 1 and 2 disclose moderate antiferromagnetic interactions mediated among the copper centers through alkoxi...

Phosphatase-like Activity of Tetranuclear Iron(III) and Zinc(II) Complexes

“…The deviations of the zinc­(II) ions from the basal planes are 0.201 Å (Zn1) and 0.176 Å (Zn2). The Zn–O bridging alkoxo bond distances [Zn1–O1, 1.965(6) Å; Zn2–O1, 1.937(5) Å] are within the range of those reported earlier, , and the values show that the Zn–O alkoxo bridge is asymmetric. The Zn–O bridging carboxylate bond distances [Zn1–O6, 2.042(5) Å; Zn2–O7, 2.020(7) Å] specify that the Zn–O succinate bridge is close to symmetric.…”

“…The present work originates from our recent interest that has been focused on the study of various multinuclear complexes of nickel, copper, and zinc with carboxylate containing polydentate ligands. − The presence of a number of carboxylate groups with flexible backbones within these ligand systems may offer further opportunities toward the formation of interesting structural frameworks. Very recently, we have explored the binding properties of two isostructural oxo-anions such as phosphate and arsenate within tetranuclear copper­(II) and zinc­(II) complexes of the ligand H 3 cpdp . Previously, a similar amide and carboxylate-based polydentate ligand has been utilized for the preparation of a self-assembled heptanuclear zinc­(II) complex displaying unusual amide binding modes .…”

“…Very recently, we have explored the binding properties of two isostructural oxo-anions such as phosphate and arsenate within tetranuclear copper(II) and zinc(II) complexes of the ligand H 3 cpdp. 35 Previously, a similar amide and carboxylate-based polydentate ligand has been utilized for the preparation of a self-assembled heptanuclear zinc(II) complex displaying unusual amide binding modes. 36 Hendrickson and co-workers 37 have reported the structural and magnetic properties of a similar tetranuclear iron(III) complex with oxo, alkoxo, and carbonato bridges.…”

Ancillary-Ligand-Assisted Variation in Nuclearities Leading to the Formation of Di-, Tri-, and Tetranuclear Copper(II) Complexes with Multifaceted Carboxylate Coordination Chemistry

“…In 1 , the two Cu(II) ions assume a distorted-square-pyramidal geometry; in 2 , two Cu(II) ions adopt a distorted-square-pyramidal geometry and the other Cu(II) ion adopts a distorted-square-planar geometry; in 3 , two Cu(II) ions exhibit a distorted-octahedral geometry, one Cu(II) ion exhibits a distorted-trigonal-bipyramidal geometry, and the other Cu(II) ion shows a distorted-square-planar geometry. Careful analyses of X-ray crystal structures show that the average Cu · · · Cu distances of 3.437, 4.723, and 3.383 Å in 1 – 3 , respectively, are significantly longer than the sum of the covalent radii of two coppers of 2.8 Å ( r cov = 1.4 Å), and hence, there is no direct Cu · · · Cu interaction . Evidently, the different Cu · · · Cu distances are caused by the various structural diversities which are due to the different coordination modes of the organic ligands.…”

“…Careful analyses of X-ray crystal structures show that the average Cu · · · Cu distances of 3.437, 4.723, and 3.383 Å in 1 – 3 , respectively, are significantly longer than the sum of the covalent radii of two coppers of 2.8 Å ( r cov = 1.4 Å), and hence, there is no direct Cu · · · Cu interaction. 72 Evidently, the different Cu · · · Cu distances are caused by the various structural diversities which are due to the different coordination modes of the organic ligands. While the occurrence of plentiful hydrogen-bonding interactions and moderate intramolecular π · · · π stacking interactions observed in 1 and 3 contribute toward the stabilization of their crystal lattices, both the hydrogen-bonding and π · · · π stacking interactions are absent in 2 .…”