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Issue 2, 2013
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Formation of two drastically different MOFs based on Mn(II)–benzoate and pyrazine with a change in seasonal temperature: structural analysis and magnetic study

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Abstract

Two new stoichiometrically and structurally very different Mn(II) coordination compounds {[Mn(pyz)(C6H5COO)2](C2H5OH)}n (1) and [Mn5(pyz)(C6H5COO)10(H2O)2]n (2) (where pyz = pyrazine) have been synthesized by the reaction of Mn(C6H5COO)2·4H2O and pyz in 1 : 1 molar ratio in different seasons of the year. The structural analyses reveal that complex 1, which is synthesized in summer when the temperature remains around 28–40 °C, features a 1D molecular ladder formed by joining of synsyn benzoate-bridged dimeric Mn(II) units by pyz. Complex 2, which is obtained in winter (temperature around 10–20 °C), is an unprecedented 2D rectangular sheet motif based on a 1D column constructed from synsyn benzoate bridged repetitive Mn5 units which are further interconnected by the pyz spacer. The compounds are interconvertible in solution: when an ethanol solution of 1 is allowed to evaporate slowly in winter or in a refrigerator (5–6 °C) it transformed into 2 whereas crystallization of 2 from ethanol medium in summer (28–40 °C) yields 1. Variable-temperature (1.8–300 K) magnetic susceptibility measurements showed presence of weak antiferromagnetic coupling in 1 that has been fitted with the van Vleck equation. The interaction in benzoate-bridged Mn2 unit was characterized to be J = −0.586(1) cm−1, where the spin-Hamiltonian is defined as H = −2JS1S2. The interaction in 2 was also characterized with the modified van Vleck equation to be weakly antiferromagnetic.

Graphical abstract: Formation of two drastically different MOFs based on Mn(ii)–benzoate and pyrazine with a change in seasonal temperature: structural analysis and magnetic study

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Publication details

The article was received on 06 Aug 2012, accepted on 22 Oct 2012 and first published on 23 Oct 2012


Article type: Paper
DOI: 10.1039/C2CE26258D
Citation: CrystEngComm, 2013,15, 400-410
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    Formation of two drastically different MOFs based on Mn(II)–benzoate and pyrazine with a change in seasonal temperature: structural analysis and magnetic study

    P. Kar, Y. Ida, T. Ishida and A. Ghosh, CrystEngComm, 2013, 15, 400
    DOI: 10.1039/C2CE26258D

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