Copper(I) Halides (X = Br, I) Coordinated to Bis(arylthio)methane Ligands: Aryl Substitution and Halide Effects on the Dimensionality, Cluster Size, and Luminescence Properties of the Coordination Polymers

Bis(phenylthio)methane (L1) reacts with CuI to yield the ID-coordination polymer [{Cu4(μ3-I)4}(μ-L1)2]n (1) bearing cubane Cu4I4 clusters as connecting nodes. The crystal structures at 115, 155, 195, and 235 K provided evidence for a phase transition changing from the monoclinic space group C2/c to P21/c. The self-assembly process of CuI with bis(p-tolylthio)methane (L2), bis(4-methoxyphenylthio)methane (L3), and bis(4-bromophenylthio)methane (L4) affords the 1D-coordination polymers [{Cu4(μ3-I)4}(μ-Lx)2]n (x = 2, 3, or 4). Compounds 2 and 4 are isostructural with C2/c low temperature polymorph of 1, whereas the inversion centers and 2-fold axes are lost in 3 (space group Cc). The use of bis(m-tolylthio)methane (L5) has no impact on the composition and overall topology of the resulting ID ribbon of [{Cu4(μ3-I)4}(μ-L5)2]n (5). Even the coordination of the sterically crowded dithioether bis(5-tert-butyl-2-methylphenylthio)-methane (L8) does not alter the network topology generating the 1D polymer [{Cu4(μ3-I)4}(μ-L8)2]n (8). The 1D polymer [{Cu(μ2-Br)2Cu}(L1)2] (9) results from the coordination of L1 with CuBr in a 1:1 metal-to-ligand ratio. In contrast to the mean Cu···Cu distances, which are <2.8 Å noted for the Cu4(μ3-I)4 clusters in the 1D polymers 1-8, the Cu···Cu contact within the Cu(μ2-Br)2Cu rhomboids of 9 [2.9194(8) Å] is above the sum of the van der Waals radii of two Cu atoms. The structural arrangement of ID polymer [{Cu(μ2-Br)2Cu}(L3)2]n (11) is quite similar to that of 9. While the reaction of CuBr with L5 results in a similar ID polymer [{Cu(μ2-Br)2Cu}(LS)2]n (12), the reaction of CuBr with L2 leads to the dinuclear complex [{Cu(μ2-Br)2Cu}(η1-L2)4] (10) ligated by four pendent bis(p-tolylthio)methane ligands. The ligation of bis(o-tolylthio)-methane, L6, on CuBr also yields a discrete complex [{Cu(μ2-Br)2Cu}(MeCN)2(η1-L6)2] (13) bearing MeCN and dangling dithioether ligands. A strong luminescence is detected for all Cul polymers, all exhibiting emission lifetimes in the microsecond time scale (i.e., phosphorescence). The polymers containing the Cu4I4 core (1-8) exhibit the typically observed low-energy band and sometimes a weaker high-energy band. The nature of the low-energy band was proposed based on literature DFT and TDDFT computations and is predicted to be a mixture of cluster-centered (CC*) and metal/halide-to-ligand charger transfer (M/XLCT). An approximate relationship between the Cu···Cu distance and the emission maxima corroborates the CC* contribution to the nature of the excited states. The emission of the rhomboid-containing materials is assigned to M/XLCT based on literature works on similar motifs.