Nitric oxide reduction of copper (II) complex with tetradentate amine ligand followed by ligand transformation (original) (raw)
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Dalton Transactions, 2012
Three copper(II) complexes, 1, 2, and 3 with L 1 , L 2 and L 3 [L 1 = 2-(2-aminoethyl)-pyridine; L 2 = 2-(N-ethyl-2-aminoethyl)-pyridine; L 3 = 3,3′-iminobis(N,N-dimethylpropylamine)], respectively, were synthesized and characterized. Addition of nitric oxide gas to the degassed acetonitrile solution of the complexes were found to result in the reduction of the copper(II) center to copper(I). In cases of complexes 1 and 2, the formation of the [Cu II -NO] intermediate prior to the reduction of Cu(II) was evidenced by UV-visible, solution FT-IR and X-band EPR spectroscopic studies. However, for complex 3, the formation of [Cu II -NO] has not been observed. DFT calculations on the [Cu II -NO] intermediate generated from complex 1 suggest a distorted square pyramidal geometry with the NO ligand coordinated to the Cu II center at an equatorial site in a bent geometry. In the case of complex 1, the reduction of the copper(II) center by nitric oxide afforded ligand transformation through diazotization at the primary amine site in acetonitrile solution; whereas, in an acetonitrile-water mixture, it resulted in 2-( pyridine-2-yl) ethanol. On the other hand, in cases of complexes 2 and 3, it was found to yield N-nitrosation at the secondary amine site in the ligand frameworks. The final organic products, in each case, were isolated and characterized by various spectroscopic studies. † Electronic supplementary information (ESI) available: See Scheme 1 Fig. 1 Ligands used for the present study. 9544 | Dalton Trans., 2012, 41, 9543-9552 This journal is Scheme 2 9546 | Dalton Trans., 2012, 41, 9543-9552 This journal is Scheme 5 9550 | Dalton Trans., 2012, 41, 9543-9552 This journal is
Dalton Transactions, 2012
Three copper(II) complexes, 1, 2, and 3 with L 1 , L 2 and L 3 [L 1 = 2-(2-aminoethyl)-pyridine; L 2 = 2-(N-ethyl-2-aminoethyl)-pyridine; L 3 = 3,3′-iminobis(N,N-dimethylpropylamine)], respectively, were synthesized and characterized. Addition of nitric oxide gas to the degassed acetonitrile solution of the complexes were found to result in the reduction of the copper(II) center to copper(I). In cases of complexes 1 and 2, the formation of the [Cu II -NO] intermediate prior to the reduction of Cu(II) was evidenced by UV-visible, solution FT-IR and X-band EPR spectroscopic studies. However, for complex 3, the formation of [Cu II -NO] has not been observed. DFT calculations on the [Cu II -NO] intermediate generated from complex 1 suggest a distorted square pyramidal geometry with the NO ligand coordinated to the Cu II center at an equatorial site in a bent geometry. In the case of complex 1, the reduction of the copper(II) center by nitric oxide afforded ligand transformation through diazotization at the primary amine site in acetonitrile solution; whereas, in an acetonitrile-water mixture, it resulted in 2-( pyridine-2-yl) ethanol. On the other hand, in cases of complexes 2 and 3, it was found to yield N-nitrosation at the secondary amine site in the ligand frameworks. The final organic products, in each case, were isolated and characterized by various spectroscopic studies. † Electronic supplementary information (ESI) available: See Scheme 2 9546 | Dalton Trans., 2012, 41, 9543-9552 This journal is
Nitric oxide reactivity of copper(II) complexes of bidentate amine ligands
Two copper(II) complexes, 1 and 2 with L1 and L2 [L1 = propane-1,3-diamine; L2 = N-isopropylpropane- 1,3-diamine], respectively, were synthesized and characterized structurally. In acetonitrile solution of the complexes, the Cu(II) centre was found to reduce in presence of nitric oxide gas. The formation of [CuII–NO] intermediate prior to the reduction of Cu(II) center was evidenced by UV–Vis, solution FT-IR, X-band EPR studies. This reduction led to the ligand transformation through diazotization at primary amine site in complex 1; whereas, N-nitrosation at the secondary amine site of the ligand was observed in 2. The final organic products were isolated and characterized by spectroscopic studies.
Inorganica Chimica Acta, 2018
In quest of copper complexes having [CuN 3 O] cores, [Cu(phen)(LVal)(H 2 O)]NO 3 (1) and [Cu(bpy)(LVal)]ClO 4 (2) complexes have been synthesized and structurally characterized (phen = 1,10phenanthroline; bpy = 2,2'bipyridine). Complex 1 possesses a distorted square-pyramidal, whereas 2 has a distorted square-planar coordination geometry. Structures of 1 and 2 have supramolecular networks formed via inter-and intra-molecular hydrogen bonding interactions. The kinetics and mechanism of ligand substitution of 1 and 2 by thiourea (TU) were studied in detail and showed a biphasic process in which an initial fast reaction is followed by a slower one. The activation parameters for the fast reaction: H # = 68 ± 4 and 73 ± 5 kJ mol-1 , S # = 43 ± 10 and 54 ± 9 J K-1 mol-1 for 1 and 2, respectively, supports a dissociative substitution mechanism. Whereas for the slow reaction: H # = 33 ± 6 and 43 ± 3 kJ mol-1 , S # =-77 ± 10 and-56 ± 9 J K-1 mol-1 for 1 and 2, respectively, support an associative substitution mechanism. It is concluded from the activation parameters that the difference in structure does not affect the mechanism. Complexes 1 and 2 have also been evaluated as functional models for the catechol oxidase enzyme and phenoxazinone synthase. The model complexes 1 and 2 show catecholase activity of K cat =10.9 x 10 3 and 11.4 x 10 3 h-1 and phenoxazinone synthase activity of K cat = 2.1 x 10 3 and 4.3 x 10 3 h-1 , respectively. Compared to the 2 | P a g e enzyme itself (K cat = 8.3 h-1), the model complexes 1 and 2 are promising candidates as functional mimics for catechol oxidase and phenoxazinone synthase.
Synthesis, Structure, and Reactivity of Model Complexes of Copper Nitrite Reductase
Inorganic Chemistry, 1996
The copper(I) and copper(II) complexes with the nitrogen donor ligands bis[(1-methylbenzimidazol-2-yl)methyl]amine (1-BB), bis[2-(1-methylbenzimidazol-2-yl)ethyl]amine (2-BB), N-acetyl-2-BB (AcBB), and tris[2-(1methylbenzimidazol-2-yl)ethyl]nitromethane (TB) have been studied as models for copper nitrite reductase. The copper(II) complexes form adducts with nitrite and azide that have been isolated and characterized. The Cu(II)-(1-BB) and Cu(II)-AcBB complexes are basically four-coordinated with weak axial interaction by solvent or counterion molecules, whereas the Cu(II)-(2-BB) and Cu(II)-TB complexes prefer to assume five-coordinate structures. A series of solid state structures of Cu(II)-(1-BB) and-(2-BB) complexes have been determined. [Cu(1-BB)(DMSO-O) 2 ](ClO 4) 2 : triclinic, P1 h (No. 2), a) 9.400(1) Å, b) 10.494(2) Å, c) 16.760(2) Å, R) 96.67(1)°,) 97.10(1)°, γ) 108.45(1)°, V) 1534.8(5) Å 3 , Z) 2, number of unique data [I g 3σ(I)]) 4438, number of refined parameters) 388, R) 0.058. [Cu(1-BB)(DMSO-O) 2 ](BF 4) 2 : triclinic, P1 h (No. 2), a) 9.304(5) Å, b) 10.428(4) Å, c) 16.834(8) Å, R) 96.85(3)°,) 97.25(3)°, γ) 108.21(2)°, V) 1517(1) Å 3 , Z) 2, number of unique data [I g 2σ(I)]) 3388, number of refined parameters) 397, R) 0.075. [Cu-(1-BB)(DMSO-O)(NO 2)](ClO 4): triclinic, P1 h (No. 2), a) 7.533(2) Å, b) 8.936(1) Å, c) 19.168(2) Å, R) 97.66(1)°,) 98.62(1)°, γ) 101.06(1)°, V) 1234.4(7) Å 3 , Z) 2, number of unique data [I g 2σ(I)]) 3426, number of refined parameters) 325, R) 0.081. [Cu(2-BB)(MeOH)(ClO 4)](ClO 4): triclinic, P1 h (No. 2), a) 8.493(3) Å, b) 10.846(7) Å, c) 14.484(5) Å, R) 93.71(4)°,) 103.13(3)°, γ) 100.61(4)°, V) 1270(1) Å 3 , Z) 2, number of unique data [I g 2σ(I)]) 2612, number of refined parameters) 352, R) 0.073. [Cu(2-BB)(N 3)](ClO 4): monoclinic, P2 1 /n (No. 14), a) 12.024(3) Å, b) 12.588(5) Å, c) 15.408(2) Å,) 101,90(2)°, V) 2282(1) Å 3 , Z) 4, number of unique data [I g 2σ(I)]) 2620, number of refined parameters) 311, R) 0.075. [Cu(2-BB)(NO 2)](ClO 4)(MeCN): triclinic, P1 h (No. 2), a) 7.402(2) Å, b) 12.500(1) Å, c) 14.660(2) Å, R) 68.14(1)°,) 88.02(2)°, γ) 78.61(1)°, V) 1233.0(4) Å 3 , Z) 2, number of unique data [I g 2σ(I)]) 2088, number of refined parameters) 319, R) 0.070. In all the complexes the 1-BB or 2-BB ligands coordinate the Cu(II) cations through their three donor atoms. The complexes with 2-BB appear to be more flexible than those with 1-BB. The nitrito ligand is bidentate in [Cu(2-BB)(NO 2)](ClO 4)(MeCN) and essentially monodentate in [Cu(1-BB)(DMSO-O)(NO 2)](ClO 4). The copper(I) complexes exhibit nitrite reductase activity and react rapidly with NO 2-in the presence of stoichiometric amounts of acid to give NO and the corresponding copper(II) complexes. Under the same conditions the reactions between the copper(I) complexes and NO + yield the same amount of NO, indicating that protonation and dehydration of bound nitrite are faster than its reduction. The NO evolved from the solution was detected and quantitated as the [Fe(EDTA)(NO)] complex. The order of reactivity of the Cu(I) complexes in the nitrite reduction process is [Cu(2-BB)] + > [Cu-(1-BB)] + > [Cu(TB)] + > [Cu(AcBB)] + .
Polyhedron, 1997
Abstraet--Cu" reacted with the polyfunctional nitroxide 4-(l'-carboxy-2'-oxopropylidene)-2,2,5,5-tetramethyl-3-imidazolidine-l-oxyl (H2L; Cu/H2L = 1:2) to yield Cu(LH)2(H20)2, which was characterized by strong fixation of water molecules exclusively by hydrogen bonds. In the interaction of Cu(LH)2(H20)2 with an additional amount of Cu" (Cu/H2L = 1 : 1), the ligands moved towards each other in parallel directions to form the binuclear compound Cu2L2(H20)5. This process is very unusual in coordination chemistry. Copyright
Asian Journal of Chemistry, 2013
A new tetradentate bis-oxime chelating ligand, 5,5'-dihydroxy-2,2'-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H4L) and its two Cu(II) complexes 1 and 2 have been synthesized by the reaction of H4L with copper(II) acetate monohydrate and copper(II) picrate tetrahydrate, respectively. The complexes have been characterized by elemental analyses, IR spectra, UV-visible spectra, TG-DTA and molar conductances. The salen-type bisoxime chelating ligand is a good tetradentate N2O2-donating ligand and the likely formulae of the Cu(II) complexes may be suggested as [Cu(H2L)]•CH3CH2OH•2H2O (1) and [Cu2(H2L)(picrate)2]•H2O (2).
European Journal of Inorganic Chemistry, 2022
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2020
Department of Chemistry, Sipajhar College, Darrang-784 145, Assam, India <em>E-mail</em>: aswinikalita2012@gmail.com <em>Manuscript received online 30 December 2019, revised 01 February 2020, accepted 29 April 2020</em> A copper(II) complex with bidentate ligand L [L, N-4-(phenylimino)pent-2-en-2-yl)benzenamine] was synthesized as its perchlorate salt. The single crystal structure for ligand L was determined as its chloride salt. The nitric oxide reactivity of the complex was studied in acetonitrile solvent. The formation of thermally unstable [Cu(II)-NO] intermediate on reaction of the complex with nitric oxide in acetonitrile solution was observed prior to the reduction of copper(II) centres to copper(I). The reduction was found to result with a mono nitrosation at the secondary amine site as well as C=C bond breaking of the ligand leads to the formation of an amide product. All the products were isolated and characterized spectroscopically. The X-ray singl...