Self-Assembly of Heterobimetallic Neutral Macrocycles Incorporating Ferrocene Spacer Groups:  Spectroelectrochemical Analysis of the Double Two-Electron Oxidation of a Molecular Rectangle

Abstract

Two Pt(4)-Fe(2) mixed-metal neutral assemblies, 4 and 5, incorporating four bis(triethylphosphine)platinum(II) centers, two flexible bridging 1,1'-ferrocenedicarboxylates, and two rigid 2,9-phenanthrenediyl (4) or 1,8-anthracenediyl (5) bridges, have been synthesized. X-ray characterization of 4 and 5 reveals the formation of discrete and highly symmetrical heterobimetallic neutral species possessing a rhomboidal and rectangular shape, respectively. The rectangular molecules, 5, could be reversibly oxidized in two two-electron steps, separated by 0.21 V. Spectroelectrochemistry in the UV-vis-NIR region confirms the ferrocene groups as primary oxidation sites; however, the intermediate 5(2+) is EPR silent even at 4 K due to enhanced EPR relaxation involving the oxidizable 1,8-anthracenediyl linkers.

Neutral discrete metal–organic cyclic architectures: Opportunities for structural features and properties in confined spaces

“…[239]. The formation of discrete and highly symmetrical heterobimetallic neutral species possessing a rhomboidal 120a and rectangular shape 120b, respectively, was confirmed by X-ray structural analysis.…”

“…Because of enhanced EPR relaxation involving the oxidizable 1,8-anthracenediyl linkers, the intermediate 120b 2+ was EPR silent, even at 4 K.The highly symmetrical neutral species of Pt metallacycles, cyclobis[(1,8-bis[trans-Pt(PEt 3 ) 2 ]anthracene)( -L99)] (121a) andScheme 47. Synthesis of metallacycles 120a and 120b[239].…”

Luminescence and Electrochemical Properties of Organostannoxane Coordination Polymer Based on Ferrocenyl-2-Cyano Carboxylate Ligand

“…Organometallic polymers have been attracting considerable attention in recent years with a view to generating new materials with interesting electrochemical, electronic and magnetic properties [1,2]. In particular, the ferrocene appended stannoxane frameworks are interest due to electrochemically inertness and do not interfere with the electrochemical properties of the peripheral ferrocene moiety [3][4][5].…”

Metallic macrocycles built-up from ferrocenedicarboxylate and ancillary nitrogen heterocycles: Hydrothermal synthesis, crystal structures and electrochemical properties

“…From the viewpoint of designing MOMs may be interesting incorporate functional ligands, which can combine flexibility with coordinating groups such as carboxylate group. Under this context we used 1,1 0 -ferrocenedicarboxylic acid which plays an important role in the field of coordination chemistry due to its diverse coordination modes such as monodentate, bidentate-chelating, tridentatebridging modes and so on [20][21][22]. In addition, it was expected by introducing a ferrocene group into coordination macrocyclic systems not only incorporates a redox-active group but also leads to interesting assembled structures due to the conformational flexibility of the ferrocene moiety such as sinperiplanar, synclinal (staggered), synclinal (eclipsed) and so on [20].…”

“…Such factors could control the size of the MOMs, where the number of components is usually controlled by the bending torsion angle of ferrocenyl moieties [16]. Finally, it is well-known that the incorporation of a secondary ligand capable to coordinate in a chelate mode is also required; such condition provides a way to the passivation of metal sites by N donors, avoiding spatial propagation of the resulting metal-organic array [21,[23][24][25][26] prepared and most of them have shown a polymeric crystal structure [20][21][22][27][28][29][30][31][32][33]. In this work we used 1,1 0 -ferrocenedicarboxylic acid with different chelate nitrogen heterocycles as ligands (2,2 0 -bipy 1,10 0 -phen and 5,5 0 -dimethyl-2,2 0 -bipy) combined with Co(CH 3 COO) 2 Á4H 2 O or Cu(CH 3 COO) 2 ÁH 2 O, which reacted under hydrothermal conditions.…”