Layered Ag(I), Cd(II) and Cu(I) Luminescent Coordination Polymers Assembled through a Tri‐pyridyl Cyclic Triimidazole Ligand

The versatility of a nitrogen rich pyridinic derivative of the cyclic triimidazole scaffold with C3 symmetry is here exploited to obtain three luminescent coordination polymers (CPs). By reaction of 3,7,11-tri(pyridin-4-yl)triimidazo[1,2-a:1',2'-c:1'',2''-e][1,3,5]triazine, (4py)3TT, with Ag(I), Cd(II) and Cu(I) salts, [Ag{(4-py)3TT}(SO3CF3)]n∙½nCH2Cl2, [Cd{(4-py)3TT}(NO3)2(EtOH)]n and [(Cu2I2)3{(4-py)3TT}4]n·xn(H2O,EtOH) are obtained. The trigonal symmetry of (4py)3TT results in 2D structures with hcb topology in [Ag{(4-py)3TT}(SO3CF3)]n∙½nCH2Cl2 and [Cd{(4-py)3TT}(NO3)2(EtOH)] and a rare 3,4-connected (3,4-c) topology in [(Cu2I2)3{(4-py)3TT}4]n·xn(H2O,EtOH). The multifaceted emissive behaviour of the CPs and the free ligand has been investigated and interpreted through spectroscopic, structural and computational studies. The fluorescence and the high energy phosphorescence of [Ag{(4-py)3TT}(SO3CF3)]n∙½nCH2Cl2, [Cd{(4-py)3TT}(NO3)2(EtOH)]n and (4py)3TT itself are correlated to singlet and triplet excited states of molecular origin while their low energy phosphorescence derives from supramolecular entities associated with strong π-π interactions with little metal contribution as is the case for the single phosphorescence observed for [(Cu2I2)3{(4-py)3TT}4]n·xn(H2O,EtOH). In agreement, unusually long lifetimes in the ms regime are measured for crystals of all compounds.