Alkyl Pyridinium Iodocuprate(I) Clusters: Structural Types and Charge Transfer Behavior

[Image: see text] The reaction of copper(I) iodide (CuI) and N-alkyl pyridinium (RPy(+), R = H, Me, Et, n-propyl = Pr, n-butyl = Bu, n-pentyl = Pn, and n-hexyl = Hx) or N-butyl-3-substituted pyridinium (N-Bu-3-PyX(+), X = I, Br, Cl, CN, and OMe) iodide salts yielded pyridinium iodocuprate(I) salts. Crystal structures of iodocuprate ions coupled with RPy(+) include {Cu(3)I(6)(3–)}(n) (R = H), {Cu(2)I(3)(–)}(n) (R = Me), {Cu(3)I(4)(–)}(n) (R = Et), {Cu(6)I(8)(2–)}(n) (R = Pr), and {Cu(5)I(7)(2–)}(n) (R = Bu, Pn, Hx). The [N-Bu-3-PyX](+) ions were typically paired with the 1-D chain {Cu(5)I(7)(2–)}(n). Diffuse reflectance spectroscopy performed on the [N-Bu-3-PyX](+) iodocuprate salts revealed that increasing the electron withdrawing capacity of the [N-Bu-3-PyX](+) system reduced the absorption edge of the iodocuprate salt. Variable temperature emission spectra of several [N-Bu-3-PyX](+) compounds revealed two emission peaks, one consistent with a cluster-centered halide to metal charge transfer and the other consistent with an intermolecular mixed halide/metal charge transfer to the organic cation. The emission intensity and emission wavelength of the mixed halide/metal to cation charge transfer depends on the organic cation substitution.