Nirmalendu Ray Chaudhuri

Synthesis, crystal structure and magnetic behavior of three polynuclear complexes: [Co(pyo)2(dca)2]n, [Co3(ac)4(bpe)3(dca)2]n and [{Co(male)(H2O)2}(H2O)]n [pyo, pyridine-N-oxide; dca, dicyanamide; ac, acetate; bpe, 1,2-bis-(4-pyridyl)ethane and male, maleate]

Three polymeric cobalt(II) complexes of formulae [Co(pyo)2(dca)2]n (1), [Co3(ac)4(bpe)3 (dca)2]n (2) and [{Co(male)(H2O)2(H2O)]n (3) [pyo, pyridine-N-oxide; dca, dicyanamide; ac, acetate; bpe, 1,2-bis-(4-pyridyl)ethane and male, maleate] have been synthesized and characterized structurally as well as magnetically. The structure determination of complex 1 shows that each octahedral Co(II) in the 1D coordination chain is attached with four μ-1,5-dicyanamide and two pendant pyridine-N-oxide ligands, which form mutual relationships with other 1D chains through non-covalent π-π interactions, giving rise to a 2D infinite sheet-like structure. The molecular structure reveals that complex 2 adopts an infinite three-leg ladder-like structure in which three parallel 1D Co(bpe) chains are connected by syn-syn and oxo bridging acetate ligands. The dicyanamide ligands are pendant to the terminal Co(II) centers. Complex 3 is an infinite 3D network in which carboxylate groups of the maleate ligand are linked to Co(II) centers in syn-anti fashion. The structure of complex 3 has already been reported. The variable temperature (300–2 K) magnetic measurements have been performed for all three complexes. In the case of 2, the full structure can be rationalized as quasi-isolated trimers; the exchange Hamiltonian that describes magnetic interactions between the effective S′ = 1/2 spins, at low temperature is . Fixing g⊥ = 6.01 and g∣∣ = 2.25, according to the EPR measurements at 4 K, 2J = −3.3 cm−1 is the best-fit parameter. For 1 and 3, complete fits are not possible for calculating the corresponding J parameters for the one- and three-dimensional structures, respectively. Only an approximate J value has been calculated for 1.

Polymeric networks of copper(II) using succinate and aromatic N–N donor ligands: synthesis, crystal structure, magnetic behaviour and the effect of weak interactions on their crystal packing

Four succinato-bridged complexes of copper(II) have been synthesized. Complex 1, [Cu(2)(mu-OH(2))(2)L(bpy)(2)(NO(3))(2)](n) and 2, [Cu(2)(mu-OH(2))(2)L(phen)(2)(NO(3))(2)](n)(bpy = 2,2[prime or minute]-bipyridine; phen = 1,10-phenanthroline and LH(2)= succinic acid) exhibit 1D coordination polymer structures where both the nitrate ions are directly linked to the copper(ii) producing synthons in a 2D sheet. A novel 2D grid-like network, ([Cu(4)L(2)(bpy)(4)(H(2)O)(2)](ClO(4))(4)(H(2)O))n3, is obtained upon changing the nitrate by perchlorate anion in complex 1, where the channels are occupied by the anions. On changing the nitrate by tetrafluoroborate anion in complex 2, a novel octanuclear complex, [Cu(8)L(4)(phen)(12)](BF(4))(8).8H(2)O 4, is isolated. The coligand bpy and phen in these complexes show face-to-face (in 1,2,3,4) or edge-to-face (in 4 )pi-pi interactions forming the multidimensional supramolecular architectures. Interestingly, the appearance of edge-to-face pi-pi interactions in complex facilitates the formation of discrete octanuclear entities. Variable-temperature (300-2 K) magnetic measurements of complexes have been done. Complexes 1 and 2 show very weak antiferromagnetic (OOC-CH(2)-CH(2)-COO) and ferromagnetic coupling (mu-H(2)O). Complex 3 also shows antiferromagnetic (syn-syn mu-OCO), and ferromagnetic coupling (mu-O of the -COO group). Complex 4 with two types (syn-syn and syn-anti) of binding modes of the carboxylate group shows strong antiferromagnetic interaction.

1D coordination polymer of copper(II) containing μ-1,1,3 azido ligand with alternating ferro–antiferromagnetic interactions

Abstract Single crystals of the copper(II) chain of formula [(μ-1,1,3-N 3 ) 2 {Cu 2 (ampy) 2 (N 3 ) 2 }] n (ampy=1-(2-aminoethyl)pyrrolidine) were prepared and characterized by X-ray diffraction methods. The copper(II) possesses the pseudo-octahedral environment with a terminal azido, one substituted alicyclic diamine and the remaining coordination occupied by N atoms of the unusual μ-1,1,3-N 3 bridging azido ligand. The magnetic behavior was investigated in the temperature range 2.0–300 K and show ferro-antiferromagnetic alternating chain. The fit of the experimental data with the expression derived for an alternating S =1/2 chains based on the exchange Hamiltonian H =−∑ N −1 i −1 [ J AF S → 2i · S → 2i +1 +J FM S → 2i · S → 2i −1 ] gave the best parameters J AF =−2.80, J FM =0.15 cm −1 , α =0.054, g =2.15 and R =1.2×10 −5 , which are consistent with a dominant antiferromagnetic coupling.

A novel layered and pillared topology in a 3D open framework: synthesis, crystal structure and magnetic properties

A one pot reaction of Cu(NO3)2, malonate dianion (mal) and 1,2-bis(4-pyridyl)ethane (bpe) leads to a novel 3D open framework, [{Cu3(mal)2(bpe)3(H2O)2}(NO3)2(H2O)2]n (1), composed of Cu–malonate layers pillared by bidentate bpe ligands encapsulating NO3− and water molecules in bidirectional intersecting channels; the frameworks secondary building unit comprises unprecedented two hexa- and four penta-coordinate copper(II) nodes which are 6- and 4-connecting, respectively, and the magnetic properties of the complex show the highest overall ferromagnetic interaction (J = 22 cm−1) of the previously reported syn–anti carboxylate bridged complexes.

Azido bridged two new ferromagnetic Cu(II) chains: synthesis, structure and magnetic behaviour

Two new polynuclear copper(II) complexes, derived from the end-to-end azido bridging ligand and two tridentate (NNN-donor) Schiff base ligands have been synthesised and their single crystal structures have been determined. They are single azido bridged chains, [Cu(L1)(μ-1,3-N 3 )] n (ClO 4 ) n ( 1 ) and [Cu(L2)(μ-1,3-N 3 )] n (ClO 4 ) n ( 2 ) where L1 and L2 are two different tridentate Schiff bases obtained from the condensation of pyridine-2-aldehyde with N, N, 2, 2-tetramethylpropane-1, 3-diamine and 1-dimethylamino-2-propylamine, respectively. Structural analyses reveal that each copper(II) centre in both the complexes are in square pyramidal geometry. The azido ligand is bridged in such a fashion that one of the nitrogens of the bridging azide is linked to equatorial of one copper(II) while the other in the axial of the neighbouring copper(II). Low temperature magnetic susceptibility data show weak intrachain ferromagnetic interaction through end-to-end azido pathway in both the complexes. The magnetic data are fitted to a high temperature series expansion for 1D system with S =1/2 local spin based on the Hamiltonian H =− J Σ S i S i+ 1 , giving the parameters J =2.69 cm −1 , g =2.10 for ( 1 ) and J =2.02 cm −1 , g =2.02 for ( 2 ).

A doubly end-to-end azido bridged 1D ferromagnetic chain

Abstract A doubly end-to-end (EE) azido bridged 1D ferromagnetic Cu(II) chain [Cu(L)2(N3)2] (1) [L=4-(dimethylamino)pyridine], representing the first observation of ferromagnetic interaction in doubly EE azido bridged chain has been synthesised and characterised by X-ray structure determination and low temperature magnetic susceptibility measurements.

A novel bimetallic alternating chain: synthesis, crystal structure and magnetic study

A novel one dimensional (1D) bimetallic polymeric complex [ catena -bis(μ- N -(aminoethyl)-3-aminopropanolato)-di-copper(II)-tetracyanonickelate(II)dihydrate] has been synthesized by the reaction of 1:1 mixture of CuCl 2 ·2H 2 O and the hydoxyamine ligand, [ N -(3-hydroxypropyl)ethane-1,2-diamine] with half equivalent of [Ni(CN) 4 ] −2 in aqueous solution. X-ray quality single crystals were obtained by slow evaporation of the ammoniacal solution of the complex. The single crystal structure reveals that it is an alkoxo bridged Cu(II) dimer linked through [Ni(CN) 4 ] 2− in trans -fashion resulting in a 1D chain. The properties of the complex have been studied by variable temperature magnetic susceptibility measurements. The susceptibility data fit well with the Cu(lI) dimer equation to give 2 J =−622 cm −1 , g =2.05. The very high coupling parameter value clearly indicates the presence of very strong antiferromagnetic interaction between the Cu(II) ions.

Synthesis, crystal structure and magnetic properties of two new dicyanamide bridged 2D and 1D complexes of Mn(II)

Two new polymeric compounds, [Mn(dca)2(4CN-py)2]n (1) and [Mn(dca)2(bpe)]n (2) where dca = dicyanamide anion, 4CN-py = 4-cyanopyridine and bpe = 1,2-bis(4-pyridyl)ethane, have been synthesised and characterised by X-ray crystallography and low temperature magnetic study. Compound 1 consists of a two-dimensional network of octahedrally coordinated Mn(II) cations bridged by dicyanamide anions. In this compound, the Mn(II) cation is linked by four dca bridging ligands and two monodentate 4CN-py ligands. Compound 2 is an one-dimensional chain of Mn(II) bridged by dca as well as bpe. Each Mn(II) in the chain is octahedrally coordinated by four dca and two bpe ligands. Variable temperature magnetic susceptibility measurements in the temperature range 300–2 K reveal the existence of weak antiferromagnetic interactions in both complexes (J = −0.154 cm−1, g = 2.01 for 1 and J = −1.25 cm−1, g = 2.00 for 2).

Two new supramolecular malonato complexes of manganese(II): synthesis, crystal structure and magnetic property

Abstract A mononuclear [Mn(mal)(bipy)(H 2 O) 2 ] ( 1 ) and a dinuclear [Mn 2 (mal)(phen) 3 (H 2 O) 2 (Cl)]Cl ( 2 ) (mal=malonate dianion; bipy=2,2′-bipyridine and phen=1,10-phenanthroline) have been synthesised and structurally characterized by X-ray crystallography. The structure of complex 1 shows that each Mn(II) is linked with one bipy, two water molecules and a malonate ligand forming distorted octahedral environment and each mononuclear fragment through H-bonding interactions form 2D supramolecular network. The structure of complex 2 comprises to an asymmetric dinuclear cation which is bridged by a single anti–anti malonate ligand and chloride anions. The two distorted Mn(II) centres are separated by large distance 6.256(3) A due to the anti–anti bridging mode. The magnetic behavior of complex 2 studied in the temperature range 300–2 K corresponds to a weak antiferromagnetic coupling through the MnOCOMn anti–anti conformation. The magnetic data were fitted based on H =−2 J S 1 ·S 2 , yielding the intramolecular coupling constant J =−0.35 cm −1 with g =1.92 and R =1.255×10 −4 .

Stabilization of the 2D inclined interpenetrated net of {[Co(bpe)(tp)(H2O)2]n by replacement of lattice water molecules with appropriate solvent

A one-pot reaction of three different components [Co(II), terephthalate dianion (tp) and 1,2-bis(4-pyridyl)ethane (bpe)] in water–methanol (1 : 1) solvent leads to the self assembly of a 2D inclined interpenetrated network of formulation {[Co(bpe)(tp)(H2O)2]·2.5(H2O)}n (1), stabilized as {[Co(bpe)(tp)(H2O)2]·(glycol)}n (2) the reaction being carried out in (1 : 1) water–glycol medium.