Red phosphorescent cuprous halide/pseudohalide coordination polymers with pyrimidine-2-thionates as Co-ligands

Hydro(solvo) thermal treatment of Cu(II) and pyrimidine-2-thione (pymtH) in the presence of halide/pseudohalide has generated four phosphorescent cuprous pyrimidine-2-thiolate complexes, namely Cu-2(pymt) Cl (1) and Cu-3(pymt)(2)(SCN) (2), Cu-3(pymt)(2)I (3) and Cu-11(pymt)(4)I-7 (4). Complex 1 has a layered structure constructed by a [Cu2SCl](infinity) staircase chain; 2 contains helical chains [Cu-3(pymt)(2)](n)(n+) that are further linked by mu(3)-1,2 kappa S:3 kappa N SCN into a 2-D layer, in which two adjacent helical chains are heterochiral; 3 is structurally related to 2 because it also contains a helical chain [Cu-3(pymt)(2)](n)(n+). Differently the helical chain in 3 is attached by iodides to form a neutral two-fold screw chain; 4 consists of linear, trigonal and tetrahedral copper(I) sites, some of which are half occupied and has a complicated layered structure. Two unprecedented coordination modes of mu 4-1 kappa S:2,3 kappa S:4 kappa N' and mu(5)-1,kappa N:2,3,4,kappa S:5,kappa N' of pymt are observed. The presence of helical [Cu-3(pymt) 2](n)(n+) chains in both 2 and 3 leads us to guess that the [Cu-3(pymt)(2)](n)(n+) chain is possibly an elementary structural species in solution. In the solid state and at ambient temperature, 1-4 all show interesting phosphorescent emissions: a strong red emission and a weak higher energy blue emission band. The weak higher energy blue emissions are tentatively assigned as originating from the halides/pseudohalides to aromatic pyrimidine pi* charge transfer while the low-energy red emissions are tentatively assigned as from ligand-to-metal charge transfer (LMCT) and/or metal-to-ligand charge-transfer (MLCT) characters, mixed with metal-centered (ds/dp) states modified by Cu-Cu interactions.