Ln() complexes with a chiral 1-pyrazolo[3,4-]pyridine derivative fused with a (−)-α-pinene moiety: synthesis, crystal structure, and photophysical studies in solution and in the solid state

• Published in: New journal of chemistry 2021-02, Vol.45 (4), p.2276-2284
• Main Authors: Bryleva, Yuliya A, Ustimenko, Yuliya P, Plyusnin, Victor F, Mikheilis, Alexsandr V, Shubin, Aleksandr A, Glinskaya, Ludmila A, Komarov, Vladislav Yu, Agafontsev, Alexander M, Tkachev, Alexey V
• Format: Article
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d0nj05277a

Chiral lanthanide( iii ) complexes, [LnL 2 (NO 3 ) 3 ]·MeCN (Ln = Sm ( 1 ), Eu ( 2 ), Tb ( 3 )), containing an optically active 1 H -pyrazolo[3,4- b ]pyridine derivative fused with a natural monoterpene (−)-α-pinene moiety (L) have been synthesized and structurally characterized. The mononuclear complexes 1-3 are isostructural and crystallize in the non-centrosymmetric space group P 2 1 2 1 2. The lanthanide ions are ten-coordinated with three bidentate chelating nitrate ions and two bidentate N,N-donor ligands L. Complexes 1-3 show metal-centered luminescence at room temperature in solution and in the solid state. The solid-state and solution-phase luminescence quantum yields increase in the order 1 < 2 < 3 . Complex 3 possesses a very high luminescence quantum yield both in acetonitrile solution ( f = 0.736) and in the solid state ( f = 0.890), indicating efficient energy transfer from two ligands L to the Ln center. The luminescence quantum yields of complexes 1 and 2 in the acetonitrile solutions are almost two and four times higher, respectively, than those in the solid state. DFT and TD-DFT studies were carried out to explore geometry and electronic structure of L and to gain insight into its absorption properties. Novel chiral luminescent Ln( iii ) complexes with a pyrazolo[3,4- b ]pyridine derivative containing a natural monoterpene (−)- α -pinene moiety are reported.