Dinuclear RhII-Phthalocyaninates with a Rh-Rh Single Bond: X-ray Crystal Structure of Di(pyridinephthalocyaninato(2-)rhodium(II))

Unbridged Rh(ii)–Rh(ii) complexes of N-heterocyclic carbenes and reactions with O2 to form dirhodium(μ–η1:η1-O2) complexes

Dimeric rhodium(ii) [Rh(L)(CH₃CN)]₂(PF₆)₄ and rhodium(iii) peroxide [Rh(L)(PPh₃)]₂(μ–η¹:η¹-O₂)(PF₆)₄ and [Rh(L)(PCy₃)]₂(μ–η¹:η¹-O₂)(PF₆)₄ (L = bis(N-pyridylimidazolylidenyl)methane) were reported.

A Theoretical Probe for Structures, Metal–Metal Bonding, and Electronic Spectra of Paramagnetic Tetrapyrrolic RuII Complex

Dimeric complexes (RuIIPz)2 have been investigated using density functional theory (DFT), where Pz is a porphyrazine ligand that features a 16-atom, 18-π-electron cyclic polyene aromatic skeleton. Structural optimizations in various configurations and spin states indicate that (RuPz)2 favours a Pz–Pz staggered conformer over an eclipsed one; the paramagnetic triplet state with the staggered configuration is found as the global ground state. This agrees with experimental magnetic results of (RuOEPor)2 (OEPor = octaethylporphyrin) and (RuPc)2 (Pc = phthalocyanine). The Ru–Ru bond length was optimized to be 2.38 Å, close to the experimental bond length of 2.40–2.41 Å. The Ru2 doubly bonded nature has been evidenced by the Ru–Ru stretching vibrational frequency of 202 cm–1, bond energy of 30.7 kcal mol–1, and electronic arrangement of σ2π4(nonbonding-δ)4(π*)2. Further confirmation was obtained from high-level wave function theory calculations (complete active space self-consistent field and n-electron valence state second-order perturbation theory). Associated with the solvation of the explicit pyridine accounting for the first coordination sphere and the implicit continuum model for the long-range interaction, the electronic spectra of tetrapyrrolic ruthenium complex were calculated at the time-dependent DFT level.

Assembled structures of tetrakis(biimidazole)dirhodium complexes hydrogen-bonded with common inorganic anions

Eight new structures of dirhodium complexes, each with four biimidazole (H2bim) ligands, were obtained: [Rh2(H2bim)4(H2O)2](NO3)4·4H2O (I), [Rh2(H2bim)4(H2O)2](ClO4)4·5H2O (II), [Rh2(H2bim)4(MeOH)2](ClO4)4 (III), [Rh2(H2bim)4(DMF)2](BF4)4 (IV), [Rh2(H2bim)4(Mepy)2](SiF6)2·8H2O (V), [{Rh2(H2bim)4(pz)}2(μ-pz)](SiF6)(ClO4)6·12.7H2O (VI), [{Rh2(H2bim)4(pz)}2(μ-pz)](ClO4)8·11.4H2O (VII) and [Rh2(H2bim)4(μ-pz)](SiF6)2·6H2O (VIII). The unbridged Rh-Rh bond distances range between 2.6313 (8) and 2.7052 (5) Å. The dirhodium units adopt a staggered conformation with torsion angles N-Rh-Rh-N of 37.6 (4)-48.98 (8)°. Various assembled structures were constructed by hydrogen bonding between the complexes and the anions: a discrete structure in (IV), one-dimensional structure in (II), two-dimensional structures in (I), (III), (VI), (VII) and (VIII) and a three-dimensional structure in (V).

The renaissance in optical spectroscopy of phthalocyanines and other tetraazaporphyrins

Spectral properties of metallophthalocyanines and other tetraazaporphyrins are governed mainly by the Q band which originates from the π-π* transitions within the ring. The position and intensity of the Q band is important in tailoring new phthalocyanine derivatives for particular applications. Aggregation, the nature of the central metal, π conjugation, symmetry of the molecules, and axial, peripheral or non-peripheral substitutions affect the spectra and hence the properties of the phthalocyanine molecule. This review gives a brief outline on how optical spectroscopy provides useful informations on molecular and electronic structures, chemistry and physics of phthalocyanines and other tetraazaporphyrins.

A One-pot, One-step, High-yield Reaction Leading to Metal–Metal Dimacrocycles: the Phthalocyanine Dimer with a Direct Si—Si Linkage

A new concept widely applicable in organometallic chemistry has been introduced for the preparation of cofacial macrocyclic dimers or oligomers. The most notable feature is the use of dimetal or oligometal salts/compounds as templates. In order to exemplify the advantage of this method, a cofacial diphthalocyanine linked by an Si—Si bond has been synthesized in 30% yield in a one-step reaction using hexachlorodisilane as a template and characterized. The cofacial dimer structures are supported by various spectroscopic techniques, including electronic absorption, magnetic circular dichroism, nuclear magnetic resonance and differential pulse voltammetry. However, the unusual phenomenon of a red shift of the main band in the Soret band region was observed.

New classes of porphyrazine macrocycles with annulated heterocyclic rings

The present contribution summarizes the most recent results on the synthesis and chemical physical characterization of the new classes of porphyrazine macrocycles having annulated five- and seven-membered heterocyclic rings, i.e. tetrakis(thiadizole)porphyrazine, TTDPzH 2, tetrakis(selenodiazole)porphyrazine, TSeDPzH 2, tetrakis-2,3-(5,7dipheny-6H-1,4-diazepino)porphyrazine, Ph 8 DzPzH 2, and a number of their metal derivatives, prepared by using, respectively, 3,4-dicyano-1,2,5-thiadiazole, 3,4-dicyano-1,2,5-selenodiazole, and 5,7-diphenyl-2,3-dicyano-6H-1,4-diazepine as monomeric precursors. The available information indicates that, owing to the presence of electron rich and soft atoms ( S , Se ) inserted in the proximity of the porphyrazine core, the TTDPz and TSeDPz macrocycles, closely resembling their phthalocyanine analogues in terms of structural and electronic features and physical behaviour (solubility, thermal stability, vaporizability, etc.), might be promising new materials for applicative properties. Particularly interesting is the operated peripheral ring opening of the TSeDPz macroxycle leading to the formation of octaaminoporphyrazine, followed by its conversion to a tetrakis(pyrazino)porphyrazine. The macrocycles containing the Ph 8 DzPz skeleton, due to the presence of the external non planar diphenyldiazepine units, appear to exhibit a distinct physical behaviour, which can be probably modulated by appropriate alternative substitutions in the 5, 6, and 7 positions of the diazepine rings.

Diphthalocyanine metal complexes and their analogues

The present overview deals with ditetrapyrrolic macrocycles, mainly diphthalocyanine systems, of the following three classes: (a) sandwich-type molecules (I); (b) metal-metal bonded systems (II); (c) single-atom bridged dimers (III). The available information focuses on the structural and electronic features, redox properties and partial oxidation. Practical applications, e.g. electrochromic devices, molecular metals, liquid crystals, non-linear optics, etc., make these classes of complexes particularly attractive and promising materials. The bonding mechanism and the structural, magnetic, conductive and optical properties of these systems are elucidated by density functional calculations.

Dimeric Osmium Phthalocyanine Organized in Discrete Columnarly Stacked Assemblies: Structure, Magnetism, and Electrical Conductivity Properties

Solid pure osmium phthalocyanine, as obtained from its adduct [PcOs(py)(2)], is an air-stable solid amorphous material. Its structure has been examined by the wide-angle X-ray scattering (WAXS) technique. Experimental data are best fitted by assuming the molecule to consist of a dimeric unit, (PcOs)(2), held together by a direct metal-metal linkage. The short Os-Os distance (2.38(1) Å) is consistent with the presence of a double bond between the two Os(II) atoms. Each Pc skeleton has a domed conformation with displacement of the respective Os atom from the plane of the four coordinating nitrogen atoms (0.40 Å) toward the other Os atom. The solid-state structure consists of disordered couples of parallel chains of (PcOs)(2). On average, six dimeric units are aligned along the stacking direction within each chain. The relative orientation of the two intradimer Pc units is 30 degrees, eclipsing occurring for the interdimer adjacent Pc units along the chain. Magnetic susceptibility measurements in the temperature range 5-300 K indicate a strong spin-spin coupling for the two metal centers in the dimer and suggest an electronic energy level sequence sigma(2)pi(4)delta(2)delta(2)pi(2) and a nonmagnetic ground state for the complex. Room-temperature electrical conductivity measurements show a sigma(RT) value of 1 x 10(-)(5) Omega(-)(1) cm(-)(1).