Chemical structure and reactions of axially coordinated iridium(III) porphyrins

Abstract

Variable valence in chemical compounds is one of the reasons of structure variety of iridium coordination compounds, in particular, complexes with tetrapyrrole ligands. Few Ir(I) porphyrin complexes are presented in the literature by several works. Among described compounds are intermediate [Ir I (CO) 3 ] 2 OEP in the course of (Cl)(CO)Ir III OEP synthesis from [Ir(cod)Cl] 2 (cod is cyclooctadiene) and H 2 OEP [1], tetracoordinated bis[iridium(I)] complex with N confused porphyrin (NCTPP) (CO) 4 (NCTPP is the dianion of N confused 5,10,15,20 tetraphenyl 21H,23H porphine) [2], and donor acceptor SAT (sitting a top) complex μ (5,10,15,20 tetraphenylpor phine) bis chloroiridium(I) [3]. Oxidation state 3+ and CN = 6 are more typical for iridium [4]. Struc tures with central Ir(III) atom were studied for com pounds of classes hexaphyrins [5], corroles [6, 7], por phyrins [8-11], and N confused porphyrins [2].According to [5][6][7][8][9][10][11], Ir(III) porphyrinoids display catalytic and redox activity, which depends on the state of axial coordination sites on the metal atom. Porphyrin complexes show distinct photoluminescent properties [12,13]. There is a rapidly growing interest in the chemistry of aromatic macroheterocyclic irid ium compounds in recent years due to the noted fea tures.The aim of this work is to study the state and reac tions of 5,10,15,20 tetraphenyl 21H,23H porphine (H 2 TPP) complexes with trivalent iridium cation (for 2 I Ir mula) in protolytic solvents AcOH and CF 3 COOH and to reveal the effect of modification at the fifth and sixth axial coordination sites in molecule on the phys icochemical properties and reactivity of the com plexes. We also obtained data for similar Re 3+ complexes presented for comparison. Only few works in the litera ture were dedicated to the physical chemistry of Re 3+ complexes with tetrapyrrole ligands: for derivatives of trans difluorophthalocyanine trans [Re(F) 2 pc 2-]and N confused porphyrin Re III (NFP)OL (P = TPP 2-) [14,15]. [16]. A mixture of H 2 TPP (0.00360 g), (Н 3 O) 2 IrCl 6 (0.01115 g) (molar ratio 1 : 5), and phenol (2.0 g) was heated under reflux for 3 h. Reaction completion was detected by the dis appearance of Н 2 ТРР in the reaction mixture using thin layer chromatography (TLC) (Silufol, chloro form). The reaction mixture was cooled, dissolved in chloroform, and washed many times with warm dis tilled water in a separating funnel to remove phenol. The chloroform solution was concentrated and chro matographed on Brockmann activity grade II alumina using chloroform as an eluent. There were three zones. The substances of the first and the third zones were purified repeatedly. Trace amounts of compound of unknown composition from the second zone were dis carded. EXPERIMENTAL (5,10,15,20 tetraphenylporphinato)chloroaquairi dium(III) (Cl)(H 2 O)Ir III TPPAbstract-Effect of modification of the axial (fifth and sixth) coordination sites on the physicochemical properties and reactivity of iridium(III) complexes with 5,10,15,20 tetraphenyl 21H,23H porphine ...