Zinc(II) complexes with Schiff bases derived from ethylenediamine and salicylaldehyde: the synthesis and photoluminescent properties

• Published in: Russian chemical bulletin 2008-09, Vol.57 (9), p.1880-1889
• Main Authors: Kotova, O. V., Eliseeva, S. V., Averjushkin, A. S., Lepnev, L. S., Vaschenko, A. A., Rogachev, A. Yu, Vitukhnovskii, A. G., Kuzmina, N. P.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Full Articles; Inorganic Chemistry; Organic Chemistry
• ISSN: 1066-5285; 1573-9171
• DOI: 10.1007/s11172-008-0254-x

The effect of the nature of organic ligands and complex formation on the photoluminescent characteristics (relative quantum yield, excited-state lifetime) and thermal stability of tetradentate Schiff bases (H 2 L), derivatives of salicylaldehyde (H 2 (SAL) 1 , H 2 (SAL) 2 ), o -vanillin (H 2 (MO) 1 , H 2 (MO) 2 ) with ethylenediamine and o -phenylenediamine, and their zinc(II) complexes was studied. Zinc(II) complexes were synthesized by the reaction of H 2 L with Zn(AcO) 2 ·2H 2 O in MeOH at room temperature or under reflux. In the case of H 2 L = H 2 (SAL) 2 , H 2 (MO) 1 , H 2 (MO) 2 , complexes of the composition ZnL·H 2 O were isolated irrespective of the temperature. For H 2 L = H 2 (SAL) 1 , the reaction results in Zn(SAL) 1 ·H 2 O at room temperature and in anhydrous dimeric complex [Zn(SAL) 1 ] 2 under reflux. Density functional calculations of H 2 L and ZnL confirmed that (1) luminescence of these compounds is due to the π-π* transition between orbitals of the organic ligand and (2) enhancement of conjugation of the chain and introduction of electron-donating substituents lead to a decrease of the energy gap and, there-fore, to a bathochromic shift of the emission maximum.