Issue 45, 2013

Copper(ii) coordination polymers of imdc (H2imdc+ = the 1,3-bis(carboxymethyl)imidazolium cation): unusual sheet interpenetration and an unexpected single crystal-to-single crystal transformation

Abstract

The monoanion of 1,3-bis(carboxymethyl)imidazolium (H2imdc+) combines with Cu(II) to produce an undulating 2D coordination polymer of composition [Cu2(imdc)2(CH3OH)2](BF4)2·(CH3OH)(H2O) (1) in which copper acetate-like dimers, linked by imdc ligands, act as 4-connecting centres. Cationic sheets stack on top of each other in an A, B, A, B… fashion and produce a structure that contains channels running parallel to the plane of network. Tetrafluoroborate anions are located in channels between sheets. Upon removal of coordinated and non-coordinated solvent molecules a single crystal-to-single crystal transformation occurs to yield a similar compound but with BF4 anions now coordinated. CO2 isotherms measured at 258 and 273 K show only modest uptake of CO2 but provide an indication that the sheets move apart at elevated pressures in order to accommodate the guest molecules. A compound of composition [Cu3(OH)2(imdc)2]·SiF6·2H2O·2MeOH (3), which possesses a 3D network, is formed by the combination of copper(II) acetate, copper(II) hexafluorosilicate and Himdc. In this structure infinite parallel Cu3(OH)2 chains are linked by bridging imdc ligands to form channels that have an approximately triangular cross-section. These channels are occupied by SiF62− anions in addition to solvent molecules. When copper(II) acetate is combined with Himdc in the appropriate ratio, a 1D coordination polymer of composition Cu(imdc)2 (4) is formed in which pairs of imdc anions bridge Cu(II) centres. When the reaction is performed in the presence of NaBF4 a minor crystalline product with tetragonal symmetry is isolated in addition to the 1D coordination polymer. This compound of composition Cu2(imdc)4NaBF4·7H2O (5) consists of 2D Cu(imdc)2 networks and features an unusual mode of interpenetration.

Graphical abstract: Copper(ii) coordination polymers of imdc− (H2imdc+ = the 1,3-bis(carboxymethyl)imidazolium cation): unusual sheet interpenetration and an unexpected single crystal-to-single crystal transformation

Supplementary files

Article information

Article type
Paper
Submitted
25 Jun 2013
Accepted
29 Aug 2013
First published
08 Oct 2013

CrystEngComm, 2013,15, 9729-9737

Copper(II) coordination polymers of imdc (H2imdc+ = the 1,3-bis(carboxymethyl)imidazolium cation): unusual sheet interpenetration and an unexpected single crystal-to-single crystal transformation

B. F. Abrahams, H. E. Maynard-Casely, R. Robson and K. F. White, CrystEngComm, 2013, 15, 9729 DOI: 10.1039/C3CE41226A

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