From 1D Helix to 0D Loop: Nitrite Anion Induced Structural Transformation Associated with Unexpected N-Nitrosation of Amine Ligand

An infinite Ag(I) coordination 4(1)-helical chain, [Ag(Hdpma)](NO3)2 center dot H2O (1), was synthesized by the self-assembly of AgNO3 and di(3-pyridylmethyl)amine (dpma). Helix 1 is 5-fold interweaved and has a topological diamondoid-like net that is extended by ligand-unsupported helix-to-helix argentophilic interactions. Two identical diamondoid-like nets with opposite chiralities interpenetrate to form the whole 3D framework as a meso compound. Typical anion-exchange reactions cause a remarkable single-crystal-to-single-crystal (SCSC) structural transformation from the 1D helix 1 to the 0D molecular loop [Ag(dpma-NO)(NO2)](2) (2) (induced by the nitrite anion, NO2-) and a 1D molecular ladder [Ag(dpma)(H2O)](NO3) (induced by the fluoride anion, F-). Molecular loop 2 is an N-nitroso compound. This work is the first to present observations of nitrite-dominated in situ N-nitrosation of an amine ligand which accompanies SCSC structural transformation via an anion-exchange reaction.