Transmetalation of a dodecahedral Na9 aggregate-based polymer: a facile route to water stable Cu(II) coordination networks.

A variety of network structures have been prepared by transmetalation of a polymer {Na3[Na9(Cbdcp)6(H2O)18]}n (1) (Cbdcp = N-(4-carboxybenzyl)-(3,5-dicarboxyl)pyridinium) containing dodecahedral Na9 aggregate secondary building units with Cu(II) by modulating the temperature, solvent, and pH. These complexes include a large, zwitterionic hexa-cuprometallocycle [Cu6(Cbdcp)6(H2O)18] (2) formed in H2O at room temperature, two three-dimensional polymers [Cu3(Cbdcp)2(OH)2(H2O)2]n (3) and {[Cu3(Cbdcp)2(OH)2]·2H2O}n (4) isolated from H2O and DMF/H2O at 135 °C, and a mononuclear complex [Cu(HCbdcp)2(H2O)3]·H2O (5) from H2O at 100 °C and pH = 6. All the complexes are robust and water stable. The crystal framework of macrocycle 2 is stable up to 100 °C under vacuum and selectively adsorbs CO2.

Stitching 2D polymeric layers into flexible interpenetrated metal-organic frameworks within single crystals.

A 2D coordination polymer prepared with bulky diethylformamide solvates exhibits channels which allow dipyridyl bridging ligands to diffuse into the crystal lattice. The absorbed dipyridyls thread through the pores of one layer and substitute the surface diethylformamide molecules on the neighboring layers to stitch alternate layers to form flexible interpenetrated metal-orgaic frameworks. The threading process also results in exchange of the bulky diethylformamide solvates for aqua to minimize congestion and, more strikingly, forces the slippage of two-dimensional layers, while still maintaining crystallinity.

A zwitterionic 1D/2D polymer co-crystal and its polymorphic sub-components: a highly selective sensing platform for HIV ds-DNA sequences.

Polymorphic compounds {[Cu(dcbb)2(H2O)2]·10H2O}n (2, 1D chain), [Cu(dcbb)2]n (3, 2D layer) and their co-crystal {[Cu(dcbb)2(H2O)][Cu(dcbb)2]2}n (4) have been prepared from the coordination reaction of a 2D polymer [Na(dcbb)(H2O)]n (1, H2dcbbBr = 1-(3,5-dicarboxybenzyl)-4,4'-bipyridinium bromide) with Cu(NO3)2·3H2O at different temperatures in water. Compounds 2-4 have an identical metal-to-ligand stoichiometric ratio of 1 : 2, but absolutely differ in structure. Compound 3 features a 2D layer structure with aromatic rings, positively charged pyridinium and free carboxylates on its surface, promoting electrostatic, π-stacking and/or hydrogen-bonding interactions with the carboxyfluorescein (FAM) labeled probe single-stranded DNA (probe ss-DNA, delineates as P-DNA). The resultant P-DNA@3 system facilitated fluorescence quenching of FAM via a photoinduced electron transfer process. The P-DNA@3 system functions as an efficient fluorescent sensor selective for HIV double-stranded DNA (HIV ds-DNA) due to the formation of a rigid triplex structure with the recovery of FAM fluorescence. The system reported herein also distinguishes complementary HIV ds-DNA from mismatched target DNA sequences with the detection limit of 1.42 nM.