A significant degree of control over the dimensionality and magnetic connectivity of Cu II carbonate coordination polymers is achieved through varying the concentration of ammonia in the reactant solution. Higher concentration leads to a two-dimensional ferromagnetic [Cu 3 (2,4′-bipy) 6 (CO 3 ) 2 ] n 2n+ kagome structure while lower concentration develops a ferromagnetic [Cu(2,4′-bipy) 2 (H 2 O) 2 ][Cu(2,4′-bipy) 2 (CO 3 ) 2 ] chain (where 2,4′-bipy = 2,4′-bipyridine). The carbonate anion in the structures arises from the fixation of atmospheric CO 2 by the basic ammonia solution. Modelling the magnetic susceptibility of 1 [a]

Three compounds consisting of pyridinium or morpholinium hydrogen oxalates each display different hydrogen oxalate hydrogen-bonding motifs, resulting in chains for 4-(di­methyl­amino)­pyridinium hydrogen oxalate 0.22-hydrate, dimers for 4-tert-butyl­pyridinium hydrogen oxalate and chains for morpholinium hydrogen oxalate.

The reaction of 1,5-dibromopentane with urotropine results in crystals of the title molecular salt, 5-bromourotropinium bromide [systematic name: 1-(5-bromopentyl)-3,5,7-triaza-1-azoniatricyclo[3.3.1.13,7]decane bromide], C11H22BrN4 +·Br− (1), crystallizing in space group P21/n. The packing in compound 1 is directed mainly by H...H van der Waals interactions and C—H...Br hydrogen bonds, as revealed by Hirshfeld surface analysis. Comparison with literature examples of alkylurotropinium halides shows that the interactions in 1 are consistent with those in other bromides and simple chloride and iodide species.