Synthesis, characterization and photoluminescence of aluminum N-aryloxo functionalized β-ketoiminate complexes

Abstract

The synthesis, characterization and luminescent properties of aluminum complexes containing a dianionic N-aryloxo functionalized β-ketoiminate ligand are presented. 4-(2-Hydroxy-5-R-phenyl)imino-2-pentanone (R = Me, L 1 H 2 ; R = tert-butyl, L 2 H 2 ) ligands reacted with AlEt 3 in tetrahydrofuran to give the aluminum complexes (L 1 AlEt) 2 (1) and (L 2 AlEt) 2 (2) in reasonable isolated yields. X-ray diffraction revealed that complexes 1 and 2 have solvent-free centrosymmetric dimeric structures, and each aluminum center has distorted trigonal bipyramidal geometry. At room temperature, complexes 1 and 2 exhibit blue photoluminescence in acetonitrile with maximum emission wavelengths of 419 and 413 nm, respectively. Chinese Sci Bull, 2011Bull, , 56: 1471Bull, −1475Bull, , doi: 10.1007 Over the past few years, β-ketoiminate ligands have become among the most attractive chelating systems in main group and transition metal coordination chemistry because of their simple preparation from inexpensive and readily available starting materials and easily modified steric and/or electronic properties. Metal complexes containing these ligand systems have been used in a variety of applications, including as precursors for metal-organic chemical vapor deposition for the growth of thin films [1] and as active catalysts in homogeneous catalysis [2][3][4][5][6][7][8][9]. However, N-aryl-oxo functionalized β-ketoimine, a derivative of β-ketoim-inate containing a pendant phenol functionality has seldom been employed in main group and transition-metal coordination chemistry [10].Recently, we began studying the synthesis and reactivity of rare earth metal complexes containing N-aryloxo func- *Corresponding authors (email: yaoym@suda.edu.cn; yanxiang@ciac.jl.cn) tionalized β-ketoiminate ligands. In our earlier work, a series of rare earth metal amides and aryloxides based on these ligand systems were synthesized and these complexes were shown to be active initiators for the ring-opening polymerization of L-lactide and ε-caprolactone [11][12][13]. In a continuation of our study in this area, herein two aluminum complexes containing N-aryloxo functionalized β-ketoiminate ligands are synthesized and their photoluminescent properties examined.

Aluminum complexes based on pyridine substituted alcohols: synthesis, structure, and catalytic application in ROP

“…Several related structures are presented in Chart 2. [57][58][59][60] At the same time it should be noted that alkyl Al complexes based on aminobis( phenolate) ONO ligands (Chart 3) are monomeric with a tetrahedral aluminum atom. 32,61 Further- Dalton Transactions Paper more, under comparison of structural features of four-coordinate (Chart 3) and five-coordinate Al complexes (for example, 3a, Fig.…”

Phosphorescent Thiazol-2-ylidene Platinum(II) Complexes with β-Ketoiminates: Single Isomer Formation by Ligand Architecture

“…Compared to typical acac ligand systems, β-ketoimines (acnac) have the advantage of applying electronic and steric effects via the (substituted) nitrogen atom while still keeping the monoanionic, bidentate ligand structure. N -Aryl-β-ketoiminates have previously been used as coordination compounds for different photoluminescent complexes with gallium (Scheme , I ) and aluminum (Scheme , II ) and in phosphorescent iridium­(III) emitters (Scheme , III and IV ) …”

“…5d,e,10 Compared to typical acac ligand systems, β-ketoimines (acnac) have the advantage of applying electronic and steric effects via the (substituted) nitrogen atom while still keeping the monoanionic, bidentate ligand structure. N-Aryl-β-ketoiminates have previously been used as coordination compounds for different photoluminescent complexes with gallium (Scheme 1, I) 11 and aluminum (Scheme 1, II) 12 and in phosphorescent iridium(III) emitters (Scheme 1, III and IV). 13 In addition, coordination compounds of platinum(II) with similar β-ketoiminate structures have been presented with interesting photophysical properties, 14 but problems of isomer formation and subsequent separation, due to the unsymmetrical nature of the β-ketoiminate ligand, were reported.…”