Reaction of 2 equiv. amount of copper(II) nitrate hexahydrate with 1 equiv. of 5-methyl-1-pyridin-2-yl-1H-pyrazole-3-carboxylic acid (PyPzCA) in presence of triethyl amine base afforded a 1D coordination polymeric compound [Cu 2(PyPzCA)2(H2O)3(NO 3)]NO3·H2O (1). Whereas, the same reaction when repeated with 1-(4,6-dimethyl-pyrimidin-2-yl)-5-methyl-1H- pyrazole-3-carboxylic acid (PymPzCA) instead of PyPzCA, a mononuclear compound [Cu(PymPzCA)]·2H2O·NEt3 (2) is formed. Both the complexes are crystallographically characterized. In 1, both the copper atoms (Cu1 and Cu2) have distorted square pyramidal geometry with N 2O3 chromophore while, in 2, the central copper atom has a distorted trigonal bipyramidal geometry with N4O chromophore. Complex 1, is a 1D coordination polymer where the metal centers being far apart and are involved in a weak ferromagnetic interaction which is quite unexpected. © 2011 Elsevier Ltd. All rights reserved.

T N MANDAL

S ROY

S GUPTA

K DAS

R SAHA

G MOSTAFA

R J BUTCHER

S K KAR

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

&nbsp;

The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

&nbsp;

It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Polyhedron

The varying coordination modes of the title ligand, L [5-methyl-1-(pyridin- 2-yl)-N′-[pyridin-2-ylmethylidene]pyrazole-3-carbohydrazide] towards the different metal centers is reported by preparation and characterization of Cu(II), Zn(II) and Cd(II) complexes, [Cu(L)NO3.H2O] (NO3) (1) [Zn(L)2](ClO4)2· 2DMF (2) and [Cd(L)(I)2] (3) respectively. In 1, the neutral ligand serves as tetradentate 4 N donor where both pyridine and pyrazole nitrogen atoms of pyridyl-pyrazole part are coordinatively active, leaving the carbonyl oxygen of the carbohydrazide part inactive. The same pyridine and pyrazole N atoms remain abstained from the coordination process towards the Zn(II) and Cd(II) metal centers. For 2 and 3 the ligand behaves as a tridentate NNO donor where the two nitrogen atoms come from azomethine, pyridine of pyridine-2-carbaldehyde parts and O from carbonyl oxygen atoms (carbohydrazide part). The complex 1 and 2 are distorted octahedral while complex 3 adopts distorted square pyramidal geometry. All the complexes are X-ray crystallographically characterized. © 2010 Elsevier Ltd. All rights reserved.

Syntheses, characterization, X-ray crystal structures and emission properties of copper(II), zinc(II) and cadmium(II) complexes of pyridyl-pyrazole derived Schiff base ligand - Metal selective ligand binding modes

Reaction of 2 equiv. amount of copper(II) chloride dihydrate with 2 equiv. of methyl-5-methyl-1-(4,6-dimethyl-2-pyrimidyl)pyrazole-3-carboxylate (DpymPzC) in presence of 1 equiv. of 2-mercapto-4,6-dimethylpyrimidine (DpymtH) at pH ∼ 6 afforded the tricoordinated copper(I) complex [Cu(DpymPzC)Cl] (1). The same reaction with copper(II) perchlorate hexahydrate, as the metal salt under the same equivalent ratio at pH ∼ 6 formed the tetracoordinated copper(I) complex [Cu(DpymPzC)2]ClO4 (2). In both the cases, the role of DpymtH is nothing but only to reduce the copper(II) salt in situ finally forming the copper(I) complex. On the other hand, the direct reaction between the copper(I) thiocyanate and DpymPzC in 2:2 equiv. ratio produced a tricoordinated copper(I) complex [Cu(DpymPzC)SCN] (3). In a similar reaction of 2 equiv. amount of copper(II) chloride dihydrate with 2 equiv. amount of ethyl-5-methyl-1-(2-pyridyl)pyrazole-3-carboxylate (PyPzC) in presence of 1 equiv. of DpymtH at pH ∼ 6, an intense red coloured microcrystalline compound (4) was obtained. In contrast, 1 equiv. of PyPzC and 2 equiv. of DpymtH on reaction with 1 equiv. of copper(II) chloride dihydrate at pH ∼ 6 produced a novel tetranuclear mixed coordinated [Cu4(DpymtH)4Cl4] complex (5). Here DpymtH plays dual role - a reducing agent for the copper(II) salt followed by a chelating ligand towards copper(I) so formed in situ. Among the above species, 1, 2 and 5 are crystallographically characterized. In 1, the central copper atom is in distorted triangular planar geometry with N2Cl chromophore whereas in 2, the same is in distorted tetrahedral geometry with N4 chromophore. Notably, the extent of distortion from the ideal geometry is more in 2. In 5, which is in chair conformation, out of four copper atoms, two being in S2Cl chromophore are tricoordinated and the remaining two are tetracoordinated with NS2Cl chromophore. The metal centers are bridged through DpymtH in its 'thione' form. Interestingly, the chelation (in part) results in formation of the highly stable four-membered two chelate rings around the two tetracoordinated copper atoms in 5. The two copper centers along the long arm of the chair are separated through a distance of 5.190 Å while those in the short arm are at a length of 3.629 Å. The electronic, IR spectra and electrochemistry of the complexes 1, 2 and 5 have also been investigated. © 2008 Elsevier B.V. All rights reserved.

Inorganica Chimica Acta

Unusual complexation of Cu(I) by pyrimidine/pyridine-pyrazole derived ligands exploiting the molecular function of 2-mercapto-4,6-dimethylpyrimidine - Syntheses, crystal structures and electrochemistry

Two mononuclear copper(II) complexes [Cu(L1)ClO4] (1), [Cu(L2)ClO4] (3) and two mononuclear vanadium(V) complexes [{VO(L1)(OCH3)(CH3OH)}{VO(L1)(OCH3)}] (2) and [VO(L2) (OCH3)(CH3OH)] (4) have been synthesized using two Schiff base ligands HL1 [N′-(2-hydroxybenzylidene)-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazide] and HL2 [1-(4,6-dimethylpyrimidin-2-yl)-N′-(2-hydroxybenzylidene)-5-methyl-1H-pyrazole-3-carbohydrazide]. These two similar ligands HL1 and HL2 in their 'ketoimine' form function as mononegative NNNO tetradentate ones towards the Cu(II) centre forming square planar part of the square pyramidal geometry. Where as the same ligands in their 'imineol' form behave as binegative ONO tridentate ones to form their V(V) analogues. In the asymmetric unit of 2, there are two independent V(V) complex molecules differing in their conformations as well as in coordination environment - octahedral V(V) in 'unit A' is hexa-coordinated while that in 'unit B' being penta-coordinated is square pyramidal. Vanadium atom in 4 is in octahedral geometry with NO5 chromophore. The ligands HL1 and HL2 have been synthesized for the first time in our laboratory and characterized by X-ray crystallography and spectroscopy. The complexes (1, 2 and 4) are also characterized by X-ray crystallography, spectroscopic and electrochemical studies. © 2008 Elsevier Ltd. All rights reserved.

Synthesis and structural characterization of copper(II) and vanadium(V) complexes of pyridyl/pyrimidyl-pyrazole derived Schiff base ligands - Metal specific adjustment of ligand binding mode

Three mononuclear cis-dioxovanadium(V) complexes of tridentate thiosemicarbazones derived from 5-methyl-3-formylpyrazole (MPA) and N(4)-methyl/ethyl/dimethyl thiosemicarbazide have been synthesized and characterized. Single crystal X-ray analyses were performed with [VO2L1] (1), [VO2L2] (2) and [VO2L3] (3), where L1, L2 and L3 denote the [1 + 1] thiosemicarbazone mono-anions derived from MPA and N(4)-substituted methyl/ethyl/dimethyl thiosemicarbazide respectively. In all the complexes the vanadium atom is in a distorted square pyramidal geometry with a N2SO2 chromophore. The interesting finding in the work is that in complexes 1 and 2, the thioimine nitrogen unusually participates in coordination whereas in 3 it is the azomethine nitrogen (quite usual) which is involved in the coordination process. © 2006 Elsevier Ltd. All rights reserved.

Synthesis and structural studies on di-oxovanadium(V) complexes of N(4)-substituted pyrazole based thiosemicarbazones

Four cis-dioxomolybdenum complexes of general formula [MoO2(Ln)EtOH] (n = 1-4) and one oxomolybdenum(IV) complex [MoO(L4)EtOH], with potentially tridentate Schiff bases derived from 5-methyl pyrazole-3-carbohydrazide and salicylaldehyde/substituted salicylaldehyde/o-hydroxy acetophenone have been prepared. The Mo(IV) complex is derived from the Mo(VI) dioxo complex by oxotransfer reaction with PPh3. The complexes are characterized by elemental analysis, electronic spectra, IR, 1H NMR, and by cyclic voltammetry. All the Mo(VI) species are crystallographically characterized. The complexes have a distorted octahedral structure in which the ligand behaves as a binegative donor one, leaving the pyrazole -N uncoordinated towards the metal center. It is also revealed from the crystal structure that the Mo(VI) center enjoys an NO5 donor environment. © 2006 Elsevier Ltd. All rights reserved.

Oxomolybdenum(VI) and (IV) complexes of pyrazole derived ONO donor ligands - synthesis, crystal structure studies and spectroelectrochemical correlation

A 1D Cu(II) coordination polymer exhibiting ferromagnetic interactions and a mononuclear Cu(II) complex of substituted pyrazole carboxylic acids: Synthesis, characterization and crystal structure

Journal	Data powered by TypesetPolyhedron
Publisher	Data powered by TypesetPERGAMON-ELSEVIER SCIENCE LTD
ISSN	0277-5387