Influence of Counteranions on the Structural Modulation of Silver–Di(3-pyridylmethyl)amine Coordination Polymers

The coordination chemistry of a flexible N-donor ligand di­(3-pyridylmethyl)­amine (dpma) with silver salts has been investigated. Six new silver coordination polymers, namely, [Ag­(dpma)­(H₂O)]­(NO₃) (<b>1</b>), [Ag­(dpma)­(CF₃CO₂)]­·1/2H₂O (<b>2</b>), [Ag­(dpma)]­(CF₃SO₃)­·1/2H₂O (<b>3</b>), [Ag­(dpma)]­(BF₄)­·3/2H₂O (<b>4</b>), [Ag₃(dpma)₂(H₂O)]­(ClO₄)₃ (<b>5</b>), and [Ag­(dpma)]­(PF₆) (<b>6</b>), have been prepared by slow diffusion reactions. All the polymeric structures of compounds <b>1</b>–<b>6</b> are described as topologic binodal networks in terms of Ag and dpma building blocks. Compounds <b>1</b>–<b>4</b> show a one-dimensional ladder-like chain structure, with both Ag and dpma as three-connected T-nodes; compound <b>5</b> is an uncommon one-dimensional metallamacrocycle-based chain structure, with Ag as two-connected I-node and dpma as three-connected T-node; compound <b>6</b> is a two-dimensional honeycomb-like layer structure, with both Ag and dpma as three-connected Y-nodes. Within the structures, the dpma ligand adopts a variety of structure conformations including gauche–trans–anti (<b>1</b> and <b>2</b>), trans–trans–anti (<b>3</b> and <b>4</b>), trans–trans–syn (<b>3</b>), gauche–gauche–syn (<b>5</b>), and trans–gauche–syn (<b>6</b>) conformations. For these Ag–dpma coordination polymers, the structural diversity and complexity are most likely attributed to the different coordinating nature, hydrogen-bonding propensity, and templating effect of the counteranions and solvent molecules. Solution studies suggest that compounds <b>1</b>–<b>6</b> would disaggregate to break down the polymeric structures and then to give multiple rapidly exchanging solution species in DMSO or acetonitrile. The thermal stabilities of compounds <b>1</b>–<b>6</b> are examined. In addition, the photoluminescent properties of compounds <b>1</b>–<b>6</b> are investigated in the solid state at room temperature

From 1D Helix to 0D Loop: Nitrite Anion Induced Structural Transformation Associated with Unexpected <i>N</i>‑Nitrosation of Amine Ligand

An infinite Ag­(I) coordination 4₁-helical chain, [Ag­(Hdpma)]­(NO₃)₂·H₂O (<b>1</b>), was synthesized by the self-assembly of AgNO₃ and di­(3-pyridylmethyl)­amine (dpma). Helix <b>1</b> 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 <b>1</b> to the 0D molecular loop [Ag­(dpma-NO)­(NO₂)]₂ (<b>2</b>) (induced by the nitrite anion, NO₂^–) and a 1D molecular ladder [Ag­(dpma)­(H₂O)]­(NO₃) (induced by the fluoride anion, F^–). Molecular loop <b>2</b> is an <i>N</i>-nitroso compound. This work is the first to present observations of nitrite-dominated in situ <i>N</i>-nitrosation of an amine ligand which accompanies SCSC structural transformation via an anion-exchange reaction