Dataset Information

Routes to new hafnium(IV) tetraaryl porphyrins and crystal structures of unusual phosphate-, sulfate-, and peroxide-bridged dimers.

ABSTRACT: New routes for the synthesis of mono tetraaryl porphyrinato hafnium(IV) complexes, Hf(IV)Por(L)(2), are reported, where the secondary ligands, L, are determined by the method of purification. These synthetic routes cater to the solubility of the macrocycles and provide access to Hf(IV) complexes of meso tetraaryl porphyrins bearing diverse functional groups such as phenyl, tolyl, pyridyl, pentafluorophenyl, and carboxyphenyl. The latter three derivatives significantly expand the repertoire of hafnium porphyrinates. One route refluxes the porphyrin with HfCl(4) in 1-chloronaphthalene or in a mixed solvent of 1-chloronaphthalene and o-cresol. A second, solventless method is also reported wherein the porphyrin is mixed with Hf(cp)(2)Cl(2) and heated to give the metalated porphyrin in good yields. Simultaneous purification and formation of stable porphyrinato hafnium(IV) diacetate complexes, Hf(Por)OAc(2), is accomplished by elution over silica gel using 3-5% acetic acid in the eluent. Exchange of the acetate ligands for other oxo-bearing ligands can be nearly quantitative, such as p-aminobenzoate (PABA), pentanoate (pent), or octanoate (oct). Notably, we find that two to three of a variety of small multitopic dianions such as peroxo (O(2)(-2)), SO(4)(-2), and HPO(4)(-2) serve to bridge between two Hf(Por) moieties to form stable dimers. The crystal structures of this library of Hf(Por) complexes are reported, and we note that careful analysis of crystallography data reveals (Por)Hf(micro-eta(2)-O(2))(2)Hf(Por) rather than four bridging oxo or hydroxy ions.

SUBMITTER: Falber A

PROVIDER: S-EPMC6195362 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Routes to new hafnium(IV) tetraaryl porphyrins and crystal structures of unusual phosphate-, sulfate-, and peroxide-bridged dimers.

Falber Alexander A Todaro Louis L Goldberg Israel I Favilla Michael V MV Drain Charles Michael CM

Inorganic chemistry 20071219 2

New routes for the synthesis of mono tetraaryl porphyrinato hafnium(IV) complexes, Hf(IV)Por(L)(2), are reported, where the secondary ligands, L, are determined by the method of purification. These synthetic routes cater to the solubility of the macrocycles and provide access to Hf(IV) complexes of meso tetraaryl porphyrins bearing diverse functional groups such as phenyl, tolyl, pyridyl, pentafluorophenyl, and carboxyphenyl. The latter three derivatives significantly expand the repertoire of ha ...[more]

PMID: 18088113

Similar Datasets

Project description:In nature, the protonation of oxo bridges is a commonly encountered mechanism for fine-tuning chemical properties and reaction pathways. Often, however, the protonation states are difficult to establish experimentally. This is of particular importance in the oxygen evolving complex of photosystem II, where identification of the bridging oxo protonation states is one of the essential requirements toward unraveling the mechanism. In order to establish a combined experimental and theoretical protocol for the determination of protonation states, we have systematically investigated a series of Mn model complexes by Mn K pre-edge X-ray absorption spectroscopy. An ideal test case for selective bis-?-oxo-bridge protonation in a Mn dimer is represented by the system [Mn(IV)2(salpn)2(?-OHn)2](n+). Although the three species [Mn(IV)2(salpn)2(?-O)2], [Mn(IV)2(salpn)2(?-O)(?-OH)](+) and [Mn(IV)2(salpn)2(?-OH)2](2+) differ only in the protonation of the oxo bridges, they exhibit distinct differences in the pre-edge region while maintaining the same edge energy. The experimental spectra are correlated in detail to theoretically calculated spectra. A time-dependent density functional theory approach for calculating the pre-edge spectra of molecules with multiple metal centers is presented, using both high spin (HS) and broken symmetry (BS) electronic structure solutions. The most intense pre-edge transitions correspond to an excitation of the Mn 1s core electrons into the unoccupied orbitals of local e(g) character (d(z)(2) and d(xy) based in the chosen coordinate system). The lowest energy experimental feature is dominated by excitations of 1s-? electrons, and the second observed feature is primarily attributed to 1s-? electron excitations. The observed energetic separation is due to spin polarization effects in spin-unrestricted density functional theory and models final state multiplet effects. The effects of spin polarization on the calculated Mn K pre-edge spectra, in both the HS and BS solutions, are discussed in terms of the strength of the antiferromagnetic coupling and associated changes in the covalency of Mn-O bonds. The information presented in this paper is complemented with the X-ray emission spectra of the same compounds published in an accompanying paper. Taken together, the two studies provide the foundation for a better understanding of the X-ray spectroscopic data of the oxygen evolving complex (OEC) in photosystem II.

Project description:Metalloporphyrin and metallophthalocyanine dyes ligating Hf(IV) and Zr(IV) ions bind to semiconductor oxide surfaces such as TiO(2) via the protruding group IV metal ions. The use of oxophylic metal ions with large ionic radii that protrude from the macrocycle is a unique mode of attaching chromophores to oxide surfaces in the design of dye-sensitized solar cells (DSSCs). Our previous report on the structure and physical properties of ternary complexes wherein the Hf(IV) and Zr(IV) ions are ligated to both a porphyrinoid and to a defect site on a polyoxometalate (POM) represents a model for this new way of binding dyes to oxide surfaces. The Zr(IV) and Hf(IV) complexes of 5,10,15,20-tetraphenylporphyrin (TPP) with two ligated acetates, (TPP)Hf(OAc)(2) and (TPP)Zr(OAc)(2), and the corresponding metallophthalocyanine (Pc) diacetate complexes, (Pc)Hf(OAc)(2) and (Pc)Zr(OAc)(2), were evaluated as novel dyes for the fabrication of dye-sensitized solar cells. Similarly to the ternary complexes with the POM, the oxide surface replaces the acetates to affect binding. In DSSCs the Zr(IV) phthalocyanine dye performs better than the Zr(IV) porphyrin dye, and reaches an overall efficiency of ~ 1.0%. The Hf(IV) dyes are less efficient. The photophysical properties of these complexes in solution suggested energetically favorable injection of electrons into the conduction band of TiO(2) semiconductor nanoparticles, as well as a good band gap match with I(3) (-)/I(-) pair in liquid 1-butyl-3-methyl imidazolium iodide. The combination of blue absorbing TPP with the red absorbing Pc complexes can increase the absorbance of solar light in the device; however, the overall conversion efficiency of DSSCs using TiO(2) nanoparticles treated with a mixture of both Zr(IV) complexes is comparable, but not greater than, the single (Pc)Zr. Thus, surface bound (TPP)Zr increases the absorbance in blue region of the spectra, but at the cost of diminished absorbance in the red in this DSSC architecture.

Dataset Information

Routes to new hafnium(IV) tetraaryl porphyrins and crystal structures of unusual phosphate-, sulfate-, and peroxide-bridged dimers.

Publications

Routes to new hafnium(IV) tetraaryl porphyrins and crystal structures of unusual phosphate-, sulfate-, and peroxide-bridged dimers.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets