Synthesis, structural, magnetic, DFT calculations and CShM studies of three new pentanuclear Mn(II) clusters.
The ditopic ligand PyPzOAPz (N-[(Z)-amino(pyrazin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid) was synthesized by in situ condensation of methyl imino pyrazine-2-carboxylate with 5-methyl-1-(2-pyridyl) pyrazole-3-carbohydrazide. In this work we have also used two of our earlier ligands PzCAP (5-methyl-N-[(1E)-1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazonic acid) (Dalton Trans., 2009, 8215) and PzOAP (N-[(Z)-amino(pyridin-2-yl)methylidene]-5-methyl-1H-pyrazole-3-carbohydrazonic acid) (Dalton Trans., 2007, 1229). These ligands PzCAP, PzOAP and PyPzOAPz were made to react with Mn(ClO(4))(2)·6H(2)O to produce three pentanuclear Mn(II) clusters [Mn(5)(PzCAP)(6)](ClO(4))(4) (1), [Mn(5)(PzOAP)(6)](ClO(4))(4) (2) and [Mn(5)(PyPzOAPz)(6)](ClO(4))(4) (3). These complexes have been characterized by X-ray structural analyses and variable temperature magnetic susceptibility measurements. All complexes have a pentanuclear core with trigonal bipyramidal arrangement of Mn(II) atoms, where, the axial metal centers have a N(3)O(3) chromophore and the equatorial centers have N(4)O(2) with an octahedral arrangement. These Mn(5)(II) clusters 1, 2 and 3 show the presence of antiferromagnetic coupling within the pentanuclear manganese(II) core (J = -2.95, -3.19 and -3.00 cm(-1) respectively). Density functional theory calculations and continuous shape measurement (CShM) studies have been performed on these complexes to provide a qualitative theoretical interpretation of the antiferromagnetic behaviour shown by them. The pentanuclear Mn(II) cluster (1) on reaction with Cu(NO(3))(2)·6H(2)O in 1:1 mole proportion in CH(3)OH:H(2)O (60 : 40) forms a homoleptic [2 × 2] tetranuclear Cu(4)(II) grid [Cu(4)(PzCAP)(4)(NO(3))(2)](NO(3))(2)·8H(2)O (4). The same Cu(4)(II) grid is also obtained from a direct reaction between the ditopic ligand PzCAP with Cu(NO(3))(2)·6H(2)O in 1:1 mole proportion. This conversion of a cluster to a grid is a novel observation.
Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata, 700 009, India.
T N
TN
Mandal
S
S
Roy
S
S
Konar
A
A
Jana
K
K
Das
S
S
Ray
S
S
Gupta
R
R
Saha
M S
MS
El Fallah
J
J
Tercero
R J
RJ
Butcher
S
S
Chatterjee
S K
SK
Kar
D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D006834:Hydrazines / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D008280:Magnetics; D059346:Magnets; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011720:Pyrazoles / Q000138:chemical synthesis / Q000737:chemistry*
D056831:Coordination Complexes; D006834:Hydrazines; D008024:Ligands; C572364:N-((Z)-amino(pyrazin-2-yl)methylidene)-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid; D011720:Pyrazoles; D008345:Manganese