Mixed-valence copper(I,II) complexes with 4-(1H-pyrazol-1-yl)-6-R-pyrimidines: from ionic structures to coordination polymers

作者：Vinogradova Katerina A; Krivopalov Viktor P; Nikolaenkova Elena B; Pervukhina Natalia V; Naumov Dmitrii Yu; Boguslavsky Evgenii G; Bushuev Mark B^*

来源：Dalton Transactions, 2016, 45(2): 515-524.

DOI：10.1039/c5dt04005a

Two pyrimidine-based ligands, 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(morpholino)pyrimidine (L-2) and 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-phenoxypyrimidine (L-3), and a series of mixed-valence copper(I,II)halide complexes, [Cu(L-2)(2)Br](2)[Cu2Br4] (1), [Cu(L-2)(2)Cl][CuCl2] (2), and [(Cu2LBr3)-Br-3](n) (3), have been synthesized. The complex [Cu(L-2)(2)Br](2)[Cu2Br4] was prepared by the reaction of L-2 with CuBr2 in a 1 : 1 molar ratio in MeCN. Its chlorido-analogue, the complex [Cu(L-2)(2)Cl][CuCl2], was synthesized by the reaction between L-2, CuCl2 and CuCl in a 2 : 1 : 1 molar ratio in MeCN. The ligand L-2 acts as a chelating one. In the structures of the complexes [Cu(L-2)(2)Br](2)[Cu2Br4] and [Cu(L-2)(2)Cl][CuCl2] the Cu2+ ion is in the cationic part of the complex whereas the Cu+ ion is located in the anionic part. The best way to synthesize the mixed-valence 1D coordination polymer [(Cu2LBr3)-Br-3] n is to react CuBr2 with L-3 in a 2 : 1 molar ratio in the MeCN/CHCl3 mixture on heating. In the structure of [(Cu2LBr3)-Br-3] n the ligand L-3 shows chelating/bridging tridentate coordination. This is the first example of the tridentate coordination of 4-(1H-pyrazol-1-yl)-6-R-pyrimidines. The striking difference between the coordination behavior of L-2 and L-3 (chelating bidentate vs. chelating/bridging coordination) is related with the possibility of rotation of the 6-phenoxy group around the C-O bond which makes the N1 pyrimidine atom less sterically hindered, enabling it to participate in metal ion binding. Importantly, all copper ions in [(Cu2LBr3)-Br-3] n show similar tetrahedral environments, CuNBr3 and CuN2Br2, which is extremely rare for mixed-valence copper(I, II) compounds. The ligands L-2 and L-3 show blue emission which is quenched upon their coordination to copper ions. The 1D coordination polymer [(Cu2LBr3)-Br-3] n shows high thermal stability and unusual solvent-occlusion properties. The role of the substituents favoring the formation of the mixed-valence copper(I,II) complexes with 4-(1H-pyrazol-1-yl)-6-R-pyrimidines is discussed.

• 出版日期2016