Synthesis, Characterization And Properties Of The Complexes Constructed From Ferrocene-based Carboxylates And N-containing Ligands

Due to the unusual properties of ferrocene and its derivatives, people have designed and synthesed many ferrocene-based ligands to produce multi-metal-containing coordination complexes, and further exploited the relationship between their structures and properties.In this paper, several ferrocene-based carboxylate-containing complexes were obtained by treating 3-ferrocenyl-2-crotonic sodium (FcC(CH₃)=CHCOONa) (Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₅), or o-ferrocecarbonyl benzoic sodium (o-FcCOC₆H₄COONa) with metal ions directly or in the presence of some subsidiary ligands. Furthermore, their syntheses, structural analysis, electrochemical and fluorescent behaviors were also studied.Firstly, the reactions of FcC(CH₃)=CHCOONa with Hg(II),Zn(II) Cd(II),Pb(II) or with 2,2'-bipyridine (2,2'-bipy) or 1,10-phenanthroline (phen) afforded complexes: [Hg(μ₂-FcC(CH₃)=CHCOO)(FcC(CH₃)=CH)]₂·CH₃OH (1)[Zn(η²-FcC(CH₃)=CHCOO)(2,2'-bipy)Cl] (2)[Cd₂Fe(μ-FcC(CH₃)=CHCOO)₂(μ₂-FcC(CH₃)=CHCOO)₂(μ₂-η²-FcC(CH₃)=CHCOO)₂(2,2'-bipy)₂]·2H₂O (3) and [Pb(μ-FcC(CH₃)=CHCOO)(μ₂-FcC(CH₃)=CHCOO)(phen)]_n (4). Complex 1 is a novel organomercury binuclear complex in which twoμ₂-FcC(CH₃)=CHCOO^- units connect two Hg(II) metal ions, and the two decarboxylato ferrocenyl productions FcC(CH₃)=CH^- inteact the Hg(II) ions as well. Complex 2 is a mononuclear complex. In complex 3, FcC(CH₃)=CHCOO^- anion acts asμ-mode,μ₂-mode orμ₂-η²-mode bridging the central Fe(II) ion and two Cd(II) cores forming a three-isonuclear complex. The structure determination of 4 reveals that FcC(CH₃)=CHCOO^-anion acts asμ-mode orμ₂-mode bridging the central Pb(II) ions forming a 1-D chain.Secondly, the treatment of o-FcCOC₆H₄COONa with Zn(II),Cd(II),Pb(II) metal ions at room temperature in the presence of N-containing ligands, such as: 2,2'-bipy, phen or 1,1'-(1,5-pentamethylene)bis-1H-benzimidazole (pbbm), obtained the single crystal of {[(o-FcCOC₆H₄COONa)·4H₂O]₂·H₂O}_n (5) and six complexes : [Zn(o-FcCOC₆H₄COO)(η²-o-FcCOC₆H₄COO)(2,2'-bipy)]·1.5H₂O (6) [Zn(o-FcCOC₆H₄COO)₂(phen)(H₂O)]·CH₃OH (7), [Zn(o-FcCOC₆H₄COO)₂(pbbm)]_n (8),[Cd(η²-o-FcCOC₆H₄COO)(μ₂-o-FcCOC₆H₄COO)(phen)]₂·CH₃OH·H₂O (9){[Cd(η²-o-FcCOC₆H₄COO)₂(pbbm)]·0.5H₂O}_n (10) and[Pb(η²-o-FcCOC₆H₄COO)(μ₂-η²-o-FcCOC₆H₄COO)(phen)]₂·CH₃OH (11). Complex 6 is amononuclear complex, in which the central Zn(II) ion is at a five-coordinated geometry. Incomplex 7, the mononuclear [Zn(o-FcCOC₆H₄COO)₂(phen)(H₂O)] units are connected byweak hydrogen bonds forming one-dimensional chain. In complex 8, each Zn atom wasconnected by two pbbm ligands, leading to an infinite one-dimensional chain, twomonodentate o-FcCOC6H4COO^- anions completed the coordination sphere of the centralZn(II) ion. Complex 9 is a binuclear cores in which the o-FcCOC₆H₄COO^- units as bridgingligands connect two Cd(II) ions. Both complexes 10 and 8 are one-dimensional polymericstructure, but the o-FcCOC₆H₄COO^- anion in 10 acts asη²-mode bridging the central Cd(II)ions. The structure determination of 11 reveals that each o-FcCOC₆H₄COO^- anion acts as atridentate fashion bridging the central Pb(II) ions forming an asymmetry binuclear complex.The electrochemical determinations of the ferrocenyl ligands and the corresponding complexes show that the half-wave potentials of ferrocenyl moieties in the complexes 1-4 are shifted to higher potential, compared with that of the free FcC(CH₃)=CHCOONa; the half-wave potentials of ferrocenyl moieties in the complexes 7-9 are also shifted to higher potential comparing with that of the free o-FcCOC₆H₄COONa. Obviously, the half-wave potential of the ferrocenyl moiety is influenced by the metal ions. The fluorescent properties of the ferrocenyl carboxylates and the corresponding complexes were aslo studied.