Syntheses of Two New 1D and 3D Networks of Cu(II) and Co(II) Using Malonate and Urotropine as Bridging Ligands: Crystal Structures and Magnetic Studies

Abstract

Two new metal-organic based polymeric complexes, [Cu(4)(O(2)CCH(2)CO(2))(4)(L)].7H(2)O (1) and [Co(2)(O(2)CCH(2)CO(2))(2)(L)].2H(2)O (2) [L = hexamethylenetetramine (urotropine)], have been synthesized and characterized by X-ray crystal structure determination and magnetic studies. Complex 1 is a 1D coordination polymer comprising a carboxylato bridged Cu(4) moiety linked by a tetradentate bridging urotropine. Complex 2 is a 3D coordination polymer made of pseudo-two-dimensional layers of Co(II) ions linked by malonate anions in syn-anti conformation which are bridged by bidentate urotropine in trans fashion. Complex 1 crystallizes in the orthorhombic system, space group Pmmn, with a = 14.80(2) A, b = 14.54(2) A, c = 7.325(10) A, beta = 90 degrees, and Z = 4. Complex 2 crystallizes in the orthorhombic system, space group Imm2, a = 7.584(11) A, b = 15.80(2) A, c = 6.939(13) A, beta = 90.10 degrees (1), and Z = 4. Variable temperature (300-2 K) magnetic behavior reveals the existence of ferro- and antiferromagnetic interactions in 1 and only antiferromagnetic interactions in 2. The best fitted parameters for complex 1 are J = 13.5 cm(-)(1), J' = -18.1 cm(-)(1), and g = 2.14 considering only intra-Cu(4) interactions through carboxylate and urotropine pathways. In case of complex 2, the fit of the magnetic data considering intralayer interaction through carboxylate pathway as well as interlayer interaction via urotropine pathway gave no satisfactory result at this moment using any model known due to considerable orbital contribution of Co(II) ions to the magnetic moment and its complicated structure. Assuming isolated Co(II) ions (without any coupling, J = 0) the shape of the chi(M)T curve fits well with experimental data except at very low temperatures.

Syntheses and crystal structures of two new coordination polymers of Cd(II) using organic spacer and inorganic-bridging ligands

“…Among the various types of anionic-bridging ligands dicyanamide [3] has been widely used due to its versatile binding modes with the metal center. Like thiocyanate [4] the another well-known anionicbridging ligand, selenocyanate [5] binds to the metal centers through Se and N. Among the well-known N-donor bridging ligands hexamethylenetetramine binds to the metal center in µ 2 or µ 4 [6,7] fashion. From the primitive age of syntheticcoordination chemistry, cadmium(II) is extensively being used in construction of new structural motifs using combination of organic and inorganic spacers due to its wide flexibility in coordination geometry.…”

3D Co(II, III) mixed-valence metal-organic framework affording field-induced slow magnetic relaxation

“…The susceptibility of 1 follows the Curie-Weiss law at temperatures above 30 K with C=15.95 cm 3 K/mol and a Weiss constant of Θ=10.91 K ( Figure S2). The high value of C and the negative Θ value may be due to the spin orbit coupling, which is remarkable for the 4 T 1g state of Co(II) in an octahedral ligand field [16]. The structure information indicates that octahedral Co(II) ions are usually Jahn-Teller distorted configurations.…”

“…The negative zJ′ value indicates the very weak antiferromagnetic coupling between the Co(II) ions. Obviously, the fit is not very good below 50 K, which is indicative of the usual problems associated with the anisotropy of the Co(II) ion [16,17]. In this case, there is an indication that the diamagnetic linkers effectively mitigates the intermolecular interaction between the metal Co(II) ions whose closest separation in the compound is 6.493 Å (Co(II)···Co(II)) [12].…”

Studies on the magnetic properties of two cobalt(II) complexes bearing 1,4-phenylenediacetate ligands

“…With the decrease in temperature, the v m T values decrease continuously, reaching a minimum of 1.74 cm 3 K mol -1 at 2.0 K. Fitting the data to the Curie-Weiss law v m = C/(T -h) above 60 K as shown in the inset of Fig. 3 gives a Curie constant of 3.48 cm 3 K mol -1 and a Weiss constant of -24.6 K. The magnetic interactions between the adjacent cobalt(II) centers in the 1D chain of [Co(P-DA)(Im) 2 a consideration of spin-orbit coupling parameter k (H = -kLS) and the crystal field strength relative to the interelectronic repulsions (A) [40][41][42][43]. …”