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A number of azacalix[2]pyrimidine[2]triazines were synthesized in moderate to good yields from both a step-wise fragment coupling approach and a one-pot reaction strategy starting from 4,6-diaminopyrimidines and cyanuric chloride. Nucleophilic aromatic substitution reaction of resulting dichloro-substituted azacalix[2]pyrimidine[2]triazines with NH4Cl led to the formation of NH2-bearing azacalix[2]pyrimidine[2]triazine analogs. Azacalix[2]pyrimidine[2]triazines adopted symmetric 1,3-alternate conformations in solution while twisted 1,3-alternate conformations were observed in the solid state. In the presence of different additives during the growth of single crystals, azacalix[2]pyrimidine[2]triazines containing amino (-NH2) groups gave varied self-assembled structures due to the formation of different intermolecular hydrogen bond motifs. [ABSTRACT FROM AUTHOR]

We herein report the synthesis and metal-directed coordination self-assembly behaviors of three new macrocyclic azacalix[4]aromatics that comprise various numbers of pyridine and pyrazine rings bridged by N-CH3 groups. Structural characterization of 1- 3 explored that their conformations are fluxional in solution and each adopts a 1,3-alternate configuration in crystalline solids. The macrocyclic skeletons in azacalixaromatic 1- 3 afford a good platform to designedly arrange coordination sites in a unique way relative to conventional multidentate ligands. Solid-state structures of three coordination self-assembled silver complexes ( 13- 15) of 1- 3 determined by X-ray crystallography suggest that the nitrogen atoms on procumbent aromatics have better coordination ability than those on perpendicular aromatics and dictate the whole coordination self-assemblies. Unique discrete and 1D chain-like structures were thus obtained. This system may afford a deeper insight into the coordination self-assembly studies of heteroatom-bridged calixaromatics, possibly extending potential application of this novel macrocyclic polydentate organic compounds in the synthesis of functional metal organic framework formation. [ABSTRACT FROM AUTHOR]