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Assembling metals $(Co^I^I and Mn^I^I)$ with pyridylcarboxylates in the presence of azide: synthesis, structural aspects and magnetic behavior of three coordination polymers

Mondal, Kartik Chandra and Oindrila, Sengupta and Nethaji, Munirathinam and Mukherjee, Partha Sarathi (2008) Assembling metals $(Co^I^I and Mn^I^I)$ with pyridylcarboxylates in the presence of azide: synthesis, structural aspects and magnetic behavior of three coordination polymers. In: Dalton Transactions (6). pp. 767-775.

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Abstract

The reaction between $Co(NO_3)_2·6H_2O$ and substituted pyridylcarboxylic acid [nicotinic acid (Hnic) or trans-3-pyridylacrylic acid (Htpa)] in the presence of $NaN_3$ under hydrothermal conditions yielded $[Co_1_._5(nic)_2 (Hnic)(N_3)]_n$ (1) and $[Co_1_._5(tpa)_2 (N_3)(H_2O)]_n$ (2), respectively. Single crystal structure analyses reveal that both complexes are 3D complicated coordination polymers. The basic repeating units in both of the complexes are $Co_3$ trinuclear clusters containing syn–syn bridging carboxylate and end-on azido linker. A similar reaction using $MnCl_2·4H_2O$ in presence of equimolar amounts of Htpa and $NaN_3$ yielded a 2D corrugated sheet $[Mn(tpa)_2]_n$ (3) containing no azide. Complex 3 can also be synthesized under hydrothermal conditions using Natpa in the absence of $NaN_3$. Surprisingly, the same reaction at room temperature yielded a known mononuclear complex $[Mn(tpa)_2(H_2O)_4]$. Variable temperature magnetic studies down to 2 K revealed the dominant antiferromagnetic nature of the first two complexes with a ferrimagnetic type of behavior despite the facts that they are homometallic and homospin systems. The susceptibility data in both cases were analyzed by a $Co_3$ trinuclear model as well as considering inter-trimer interactions. Complex 3 is weakly antiferromagnetic in nature with an exchange parameter of J =−2 $cm^-^1$ through the syn–anti bridging carboxylate pathway.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to The Royal Society of Chemistry
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 04 Mar 2008
Last Modified: 19 Sep 2010 04:43
URI: http://eprints.iisc.ernet.in/id/eprint/13295

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