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Amino alcohols and benzoates-Friends or foes? Tuning nuclearity of Cu(II) complexes, structures, magnetism, DFT and TD-DFT studies, and catecholase like activities

Abstract

The coordination chemistry of a series of Cu(II) complexes of various aminoalcohol and benzoate ligands is explored. The pH dependent reactions of copper(II) salts with propanolamine (Hpa), N-methyl diethanolamine (H2mdea), triethanolamine (H3tea) and nbutyl-diethanolamine (H2budea) are carried out in presence of various benzoates (benzoic acid, 2-hydroxy benzoic acid, 4-hydroxy benzoic acid, 3-methoxy benzoic acid and 4-methoxy benzoic acid). The resulting complexes, [Cu2(pa)2(benzoate)2] (1), [Cu2(pa)2(3-methoxybenzoate)2] (2), [Cu2(pa)2(4-methoxybenzoate)2] (3), [Cu2(H2tea)2(benzoate)2]•2H2O (4), [Cu2(H2tea)2(2-hydroxybenzoate)2]•2H2O (5), [Cu2(H3tea)2(4-hydroxybenzoate)2][Cu(Htea)2]•2H2O (6), [Cu(H2mdea)2][benzoate]2 (7), [Cu(H2mdea)2][4-methoxybenzoate]2 (8), [Cu(H2bdea)2][2-hydroxybenzoate]2 (9), [Cu2(benzoate)4(benzoic acid)2] (10), [Cu2(4-methoxybenzoate)4(CH3CN)2]•4CH3CN (11) and [Cu3(H2tea)2(benzoate)2(NO3)2] (12) are formed as mono-, di- or trinuclear entities depending upon the pH condition of the reaction. The complexes are characterized employing spectral, magnetic, single crystal X-ray and DFT/TDDFT studies. 7 and 8 exhibit emission peaks at 510 and 460 nm, respectively, in the solid state photoluminescence (PL) spectra. The temperature variable magnetic properties of 1‒12 reveal the presence of antiferromagnetic (in 1‒3 and 7‒11) or ferromagnetic interactions (in 4‒6 and 12) with Curie constant, C = 0.24 (7), 0.28 (8) or 0.35 cm3 K mol‒1 (9) and a Weiss constant, θ = ‒0.34 (7), ‒0.32 (8) or ‒0.40 (9) K for mononuclear complexes. The dinuclear complexes have J = ‒89.2(2) (1), ‒71.1(3) (2), ‒59.6(1) (3), 98(1) (4), 79.1(2) (5), ‒85.4(2) (10) and ‒89.5(2) (11) cm‒1. Strong ferromagnetic interactions are observed in case of 6 (J = 172 (3) cm‒1 and zJ′ = 2.3(2) cm‒1), which are comparable with those of 12 (J12 = 197(2) cm−1, J13 = −9.3(3) cm−1). A correlation exists between the Cu‒O‒Cu angle and magnetic coupling in di- and trinuclear Cu(II) complexes. Moreover, 4‒6 are active catalysts for the oxidation of 3,5-DTBC to 3,5-DTBQ and show catecholase activity in the order 4>5>6 (Kcat = 943 (4), 698 (5) and 553 h‒1 (6)). This order can be rationalized in terms of the electron density on the ligand which neutralizes the effective positive charge on Cu(II) thus forming the less or more stable intermediate. Order of catecholase activity and electronic spectral properties of 4‒6 are also investigated by DFT and TD-DFT studies, respectively.

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Publication details

The article was received on 29 Apr 2017, accepted on 15 Jun 2017 and first published on 15 Jun 2017


Article type: Paper
DOI: 10.1039/C7DT01571B
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Amino alcohols and benzoates-Friends or foes? Tuning nuclearity of Cu(II) complexes, structures, magnetism, DFT and TD-DFT studies, and catecholase like activities

    F. Sama, A. K. Dhara, M. N. Akhtar, Y. Chen, M. Tong, M. Shahid, I. A. Ansari, M. Raizada, M. Ahmad and Z. A. Siddiqi, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT01571B

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