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A metal-organic framework (MOF), NH(2)-MIL-101(Al), which acts as a bifunctional, site-isolated Lewis acid-Brønsted base heterogeneous catalyst, catalyzes a tandem Meinwald rearrangement-Knoevenagel condensation reaction with remarkable substrate selectivity.

Four 2D helical coordination polymers (CPs) (1-4) were synthesized using achiral 2,6-bis (imidazol-1-yl)pyridine (pyim 2) ligand with metal nitrates (metal = zinc and cadmium), which showed that variation in the solvent condition leads to difference in geometry around the central metal ion and results in chiral/achiral behaviour of these CPs. By using (pyim 2), [trans-Zn(pyim 2) 2 (NO 3) 2 ] n (1) was obtained by unary solvent (MeOH), while [trans-Cd(pyim 2) 2 (NO 3) 2 ] n (2) was formed under binary solvent mixtures (DMF/MeOH). On the other hand, in ternary solvent mixture (DMF/MeOH/H 2 O) it resulted into an achiral {[trans-Zn(pyim 2) 2 (H 2 O) 2 ]•(NO 3) 2 } n (3) and homochiral {[cis-Cd(pyim 2) 2 (H 2 O) 2 ]•(NO 3) 2 } n (4) coordination polymer, respectively. The homochiral behaviour of the coordination polymer (4) was further studied by solid state CD spectra and also its optical behaviour was analyzed by polarimetry.

An anion triggered single-crystal-to-single-crystal (SCSC) transformation was observed from 1D to 2D by counteranion exchange from PF 6 − to NO 3 − and vice versa. In addition, the cause for SCSC transformation involving the metal-ligand bond breaking/formation phenomenon and enhancement/decrement of the network dimensionality is discussed. The anion/solvent exchange transformations were confirmed directly through single crystal X-ray diffraction, IR spectroscopy, PXRD and elemental analysis. Furthermore, the thermal and solid state photoluminescence properties of 1-4 were analyzed.CrystEngComm This journal is