No abstract

We report on the photoluminescence of {CuSCN(3-XPy)2}n crystals (X = Br, Cl; Py = pyridine). Laser excitation at 266 nm for CuSCN(3-BrPy)2 at 78 K results in a decrease in the luminescence intensity with increasing irradiation time. Heating the sample to 298 K and recooling to 78 K results in recovery of the original luminescence intensity, hence manifesting an optical memory effect. Laser irradiation at longer or shorter wavelengths fails to produce a reduction in emission intensity. Interestingly, CuSCN(3-ClPy)2, despite being isomorphic, does not undergo emission intensity changes regardless of laser irradiation wavelength variation. Density Functional Theory (DFT) and Time Dependent DFT (TD-DFT) calculations were performed on an adjacent chain model to explore the photochemical change that occurs upon laser irradiation. The observed reduction in luminescence intensity is attributed to photo-induced electron transfer quenching in which Cu(I) is oxidized to a non-luminescent Cu(II) with capture of the halogen by a neighboring SCN ligand on the adjacent coordination polymer chain.

A total of five new CuSCN-L compounds with alkyl sulfide ligands, L = methyl sulfide (Me 2 S), ethyl sulfide (Et 2 S), isopropyl sulfide (Pr i 2 S) or tetrahydrothiophene (THT) have been prepared and characterized. X-ray crystal structures for four of the compounds were obtained. Two compounds were collected from solutions of CuSCN in Me 2 S: {[Cu(SCN)(Me 2 S) 2 ]} n (1a) in the form of colorless blocks and (CuSCN)(Me 2 S) (1b) as a white powder. Neat mixtures of CuSCN in the other alkyl sulfide ligands yielded only one product each: {[Cu(SCN)(Et 2 S)]} n (2); {[Cu(SCN)(Pr i 2 S)]} n (3); and {[Cu(SCN)(THT) 2 ]} n (4). Crystals of 2 and 4 underwent destructive phase changes at lower temperatures. Two networks types were observed: 1:2 decorated 1-D chains (1a and 4) and 1:2 decorated 1-D ladders (2 and 3). Further network formation through bridging of the organic sulfide ligands was not observed.