Silver Coordination Polymers Based on Newly Designed Bis(cyanobenzyl)bipiperidine Ligand: Synthesis, Anion Exchange, Guest Inclusion, Electrochemical, and Photoluminescence Properties

A new flexible ligand, bis(cyanobenzyl)bipiperidine (L), has been synthesized and structurally characterized. Nine novel silver(I) coordination polymers (CPs), the dimensionality of which depends on the counter anion, [Ag-2(L)(NO3)(2)](n) (1), [Ag-2(L)(NO3)(2)](n) (2), [Ag-2(L)-(NO3)(2))] (C16H10)} (3), {[Ag-2(L)(NO3)(2))](C20H12)} (4), [Ag-2(L)(ClO4)(2)](n) (5), [Ag-2(L)(CF3SO3)(2)(C4H8O)(2)](n) (6), [Ag-2(L) (CF3SO3)(2)(C3H6O)(2)](n) (7), {[Ag-2 (L)(2)]center dot(BF4)center dot 2-(C3H6O)}(n) (8), and [Ag-2(L)(3)(PF6)(2)]center dot x(C3H6O) (9), have been prepared by self -assembly of L with AgX (X = NO3-, ClO4-, CF3SO3-, BF4-, and PF6-) and aromatic guest molecules. Reactions of L with AgNO3 in acetone in either 1:2 or 1:1 stoichiometric ratio occurred rapidly at room temperature, yielding topologically different structural isomers of the three-dimensional (3D) CPs 1 and 2. Additional reactions of linker L with AgNO3 in the presence of aromatic guest molecules (pyrene, perylene) formed CPs of 3 and 4 with the inclusion of the corresponding guest in the crystal lattice associated with the reduction of dimensionality of the self -assembled product from 3D to two-dimensional (2D). Reaction of L with AgTf (Tf = CF3SO3-) in acetone and THE gave two structurally related 2D CPs (6 and 7). Compound 8 represents a one-dimensional (1D) coordination polymer where the BF4 anions are not linked to the silver nodes, while 9 is a discrete coordination complex. Anion exchange accompanying an irreversible structural conversion from 7 to 1 and 7 to 8 was monitored in the crystalline state by IR and PXRD techniques. On the other hand, a reversible anion exchange process was observed between 1 and 8. The electrochemical and solid-state photoluminescence properties of these Ag(I) CPs were also characterized.