Benzothiadiazolyl‐pyridine and ‐2,2′‐bipyridine Ligands for Luminescent and Magnetic Complexes

Abstract

Two new luminescent ligands, 4‐(2‐pyridine)‐7‐methyl‐2,1,3‐benzothiadiazole (L1) and 4‐(2,2‐bipyridine)‐7‐methyl‐2,1,3‐benzothiadiazole (L2), based on 2,1,3‐benzothiadiazole and pyridine or bipyridine were obtained by Suzuki coupling reactions. DFT and TD‐DFT type calculations have been performed on L1 and L2 in order to assign their experimental UV‐visible and emission bands. Reaction of L1 and L2 with metal(II) chlorides (M = Zn, Mn, Cu) provided the neutral complexes of formulas [ZnL1Cl2] (1), [Zn(L1)2Cl2] (2), [ZnL2Cl2] (3), [MnL2Cl2]·0,5CH2Cl2 (4) and [CuL2Cl2]·H2O (5) which have been structurally characterized. The Zn(II) ions in 1 and 2 are four‐coordinate in somewhat distorted tetrahedral N2Cl2 surroundings with L1 adopting bidentate (1) and monodentate (2) coordination modes. Complexes 3‐5 are isostructural and their metal atoms are five‐coordinate in distorted square pyramidal environments with three nitrogen atoms from the tridentate L2 ligand and a chlorine building the basal plane and another chlorine atom occupying the apical position. The three Zn(II) complexes are strongly luminescent in solution and the solid state, while the cryomagnetic study of the paramagnetic compounds 4 and 5 in the temperature range 2.9‐300 K shows a Curie‐Weiss behaviour typical of small antiferromagnetic interactions which are mediated by weak intermolecular contacts.

Six-coordinated nickel(ii) complexes with benzothiadiazole Schiff-base ligands: synthesis, crystal structure, magnetic and HFEPR study

“…[18][19][20][21][22][23][24] Ligands based on the 2,1,3-benzothiadiazole (BTD) unit, which is a well-known electron acceptor fluorophore, 25 were mostly used for obtaining luminescent metal complexes. [26][27][28][29] On the other hand, our recently reported Schiff base ligands based on BTD, as products of condensation of 4-amino-2.1.3benzothiadiazole and salicylaldehyde (HL 1 ) or ortho-vanillin (HL 2 ) (Chart 1) provided several metal complexes. For example, the copper complexes [CuL 1 (hfac)] and Cu(L 2 ) 2 30 show very weak intermolecular antiferromagnetic interactions in the low temperature region and the neutral [CoL with L 2 exhibit slow relaxation of the magnetization under dc applied magnetic field, characteristic of single-ion magnet (SIM) behaviour.…”