Experimental and theoretical studies of the ancillary ligand (E)-2-((3-amino-pyridin-4-ylimino)-methyl)-4,6-di-tert-butylphenol in the rhenium(i) core

Abstract

The fac-[Re(CO) 3 (deeb)L] + complex (C2) where L is the (E)-2-((3-amino-pyridin-4-ylimino)-methyl)-4,6di-tert-butylphenol ancillary ligand, which presents an intramolecular hydrogen bond, has been synthesized and characterized using UV-vis, 1 H-NMR, FT-IR, cyclic voltammetry and DFT calculations.The UV-vis absorption and emission properties have been studied at room temperature and the results were compared with TDDFT calculations including spin-orbit effects. We report an alternative synthesis route for the fac-Re(CO) 3 (deeb)Br (C1) complex where deeb = (4,4 0 -diethanoate)-2,2 0 -bpy. Besides, wehave found that the C1 shows a red shift in the emission spectrum due to the nature of the ancillary electron donating ligand, while the C2 complex shows a blue shift in the emission spectrum suggesting that the ancillary ligand L has electron withdrawing ability and the importance of the intramolecular hydrogen bond. The calculations suggest that an experimental mixed absorption band at 361 nm could be assigned to MLCT and LLCT transitions. The electron withdrawing nature of the ancillary ligand in C2 explains the electrochemical behavior, which shows the oxidation of Re I at 1.83 V and the reduction of deeb at À0.77 V. 1.44 [s, 6H, (-CH 3 )], 4.49 [m, 4H], 5.92 [s, 2H, -NH 2 ], 6.45 [d; J = 5.5 Hz; 1H], 7.28 [d; J = 1.5 Hz; 1H], 7.47 [s, 1H], 7.51 [s, 1H], 7.53 [s, 1H], 8.11 [s, 1H], 8.20 [d; J = 5.5 Hz; 2H], 8.91 [s, 2H], Scheme 1 Structures of deeb and L ligands used in this work.

Fluorescence probes for prokaryotic and eukaryotic cells using Re(CO)3+complexes with an electron withdrawing ancillary ligand

“…The ancillary ligand L was synthesized according to literature [35][36][37][38]. All starting materials were purchased from Merck and Aldrich and used without further purification.…”

“…were prepared by reacting bromotricarbonyl(tetrahydrofuran)rhenium (I) dimer as described [37]. The synthesis of (E)-2-((3-amino-pyridin-4-ylimino)-methyl)-4,6-diterbutylphenol L was previously reported by Kleij et al [35][36] and its electronic, biological and others properties were reported by…”

“…Carreño et al [37][38] Rhenium(I) tricarbonyl complexes with the following general configuration [Re(CO) 3 where X is a monodentate ligand like phosphine such as mer-trans-bromo-tricarbonyI-bis(diphenylmethyl-phosphÍnite)rhenium(I), presents meridional isomeric form had been reported. [60] A characteristic properties of mer-isomers is the very low IR intensity of the highest frequency band with respect to the other two bands, which is not observed for C1 and C2.…”

“…Several studies on biological systems have shown that an intramolecular hydrogen bond (IHB) in amino acids, like histidine, is involved in the electron transport chain by the formation of phenoxy radicals [30][31][32][33]. (E)-2-((3-aminopyridin-4-ylimino)-methyl)-4,6-di-tert-butylphenol (L)] as ancillary ligand [35][36][37][38][39]. In this context, we have described and alternative and improved synthesis, along with its chemical characterization, of a Rhenium (I) tricarbonyl complex presenting a Schiff base harboring an IHB [i.e.…”

“…In this work, we report an alternative synthesis of fac-Re(CO) 3 (bpy)Br (C1) and fac-Re(CO) 3 (dmb)Br (C2) precursors [41][42][43][44][45][46], where bpy is a 2,2'bipyridine and dmb is 4,4'-dimethyl-2,2'-bipyridine, starting from bromotricarbonyl(tetrahydrofuran)rhenium(I) dimer (Re(CO) 3 Br(THF)) 2 at room temperature [37]. In this work, we report an alternative synthesis of fac-Re(CO) 3 (bpy)Br (C1) and fac-Re(CO) 3 (dmb)Br (C2) precursors [41][42][43][44][45][46], where bpy is a 2,2'bipyridine and dmb is 4,4'-dimethyl-2,2'-bipyridine, starting from bromotricarbonyl(tetrahydrofuran)rhenium(I) dimer (Re(CO) 3 Br(THF)) 2 at room temperature [37].…”