Coordination variability of CuI in multidonor heterocyclic thioamides: synthesis, crystal structures, luminescent properties and ESI-mass studies of complexes

Abstract

The chemistry of copper(I) with scarcely investigated heterocyclic thioamides, particularly 2,4,6-trimercaptotriazine, purine-6-thione, 2,4-dithiouracil, 2-thiouracil and pyrimidine-2-thione is described. The interaction of 2,4,6-trimercaptotriazine (tmtH₃) with [Cu(CH₃COO)(PPh₃)₂] resulted in a pair of bond isomers: [Cu(κ¹N-tmtH₂)(PPh₃)₂] (6a), [Cu(κ¹N,κ¹S-tmtH₂)(PPh₃)₂] (6b); with copper(I) bromide and PPh₃, it formed a trinuclear complex, [Cu₃Br₂(κ¹N,κ¹S, μ-S-tmtH₂)(PPh₃)₆] (7) with anionic tmtH₂⁻. The 2,4-dithiouracil with copper(I) halides (CuCl, CuBr) and PPh₃ yielded dinuclear complexes: [Cu₂(μ-Cl)(κ¹S,κ¹S-dtucH)(PPh₃)₄] (4) and [Cu₂(μ-Br)(κ¹S,κ¹S-dtucH)(PPh₃)₄] (5) with unusual eight-membered metallacyclic rings. Pyrimidine-2-thione (pymSH) is an N,S-chelated anion in a mononuclear complex, [Cu(κ¹N,κ¹S-pymS)(PPh₃)₂] (1), whereas 2-thiouracil (tucH₂) with copper(I) chloride and PPh₃ yielded a tetrahedral complex, [CuCl(κ¹S-tucH₂)(PPh₃)₂] (3). Purine-6-thione (purSH₂) coordinated to Cu^I in two different modes yielding mono- and di-nuclear complexes, [Cu(κ¹N,κ¹S-purS)(PPh₃)₂]·CH₃OH (2a) and [Cu₂(κ¹N,μ-S-purS)₂(PPh₃)₂] (2b). The existence of bond isomers (6a and 6b), synthesis of novel dinuclear (4 and 5) and rare trinuclear (7) complexes with unusual bonding patterns are the novel features of the present study. Complexes show intense emission bands in the 380–530 nm region with λ_em at 490 to 495 nm.