Studies on Cage‐Type Tetranuclear Metal Clusters with Ferrocenylphosphonate Ligands

Abstract

Reaction of FcCH(2)PO(3)H(2) [Fc=(eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4))] (H(2)FMPA) and 1,10-phenanthroline (phen) with Cd(OAc)(2).2 H(2)O or ZnSO(4).7 H(2)O in methanol in the presence of triethylamine resulted in the formation of two new ferrocenylphosphonate metal-cage complexes [M(4)(fmpa)(4)(phen)(4)] 7 CH(3)OH (M=Cd 1, M=Zn 2). Both structures contain two kinds of isomeric tetranuclear metal phosphonate cages, which are linked to one another by pi-pi interactions between the phen molecules. In 1, the Cd1, Cd3, and Cd4 atoms are all pentacoordinate, while the Cd2 atom is coordinated by four oxygen atoms from three phosphonate ligands and two nitrogen atoms from the chelating phen in a distorted octahedral geometry. Four Cd atoms from each unit are interconnected through bridging phosphonate ligands with different coordination modes, such as 5.221, 4.211, and 2.11 (Harris notation), yielding a {Cd(4)} cage. In 2, each Zn atom is coordinated by three oxygen atoms from three phosphonate ligands and two nitrogen atoms from phen, leading to a distorted square-pyramidal geometry. The four Zn atoms of each isomeric unit are also interconnected through four bridging phosphonate ligands to yield a {Zn(4)} cage. Fluorescent studies indicate that ligand-to-ligand charge-transfer photoluminescence is observed for 1, while the emission bands of 2 can be assigned to an admixture of ligand-to-ligand and metal-to-ligand charge transfer. Solution-state differential pulse voltammetry indicates that the half-wave potentials of the ferrocenyl moieties in 1 and 2 have different deviations relative to the relevant H(2)FMPA ligand. This may be because the highest occupied molecular orbital (HOMO) in 1 is located in the FMPA(2-) groups, while in 2 the HOMO is located in the phen and Zn(II) groups, so the Fe(II) centers in complex 1 are more easily oxidized to Fe(III) centers than those of 2. The third-order nonlinear optical (NLO) measurements show that both 1 and 2 exhibit strong third-order NLO self-focusing effects; hence, they are promising candidates for NLO materials. By calculating the component of the lowest unoccupied molecular orbitals of 1 and 2, we confirmed that the co-planar phen rings control their optical nonlinearity, while the H(2)FMPA ligands and metal ions have only a weak influence on their NLO properties.

Auxiliary aromatic-acid effect on the structures of a series of ZnII coordination polymers: Syntheses, crystal structures, and photoluminescence properties

“…5c. Although a large number of high-connected structures have been documented [44][45][46][47], to our knowledge, (3,4,8)connected framework has been not reported until now.…”

“…pentanuclear metal clusters, therefore, pentanuclear metal cluster is defined as an eight-connected node, while each Zn4 connecting two BTEC ligands and one L ligand acts as a 3-connected node, each BTEC ligand bridging two pentanuclear metal clusters and two Zn4 ions acts as a 4-connected node. So the whole framework can be described as a (3,4,8)-connected network with the Schläli symbol of (4 Á 6 2 )(4 2 Á 6 3 Á 8)(4 2 Á 6 4 )(4 2 Á 6 18 Á 7 Á 8 6 Á 10), as shown in Fig. 5c.…”

“…Although a variety of MOFs with beautiful topologies and interesting properties have been synthesized to date, rational control in the construction of polymeric networks still remains a great challenge in crystal engineering. From the viewpoint of crystal engineering, the most effective and facile approach to overcome this is the appropriate choice of the well-designed organic bridging ligands (building blocks) containing modifiable backbones and connectivity information, together with the metal centers (nodes) with various coordination preferences [7][8][9]. Multidentate N-or O-donor ligands have been investigated extensively as organic spacers in the construction of MOFs.…”

Novel ferrocenyl phosphonate derivatives. Inhibition of serine hydrolases by ferrocene azaphosphonates

“…[5] Ferrocene compounds containing a phosphonate moiety are of interest owing to their electrochemical properties and their ability to strongly bind to metal oxide solid supports. [6] Interestingly, no data have been reported so far on the biochemical activity of these molecules, in particular their ability to inhibit serine hydrolases.…”

The phospha-Michael addition of dimethyl- and diphenylphosphites to the η1-N-maleimidato ligand: Inhibition of serine hydrolases by half-sandwich metallocarbonyl azaphosphonates

“…This feature enables immobilization of organometallic moieties (e.g. redox-active ferrocenyl groups) on robust inorganic backbones, which may be of interest for many branches of materials science [2]. On the other hand, phosphonates having azaheterocyclic substituents may manifest interesting biological activities [3].…”