Electrochemical, Computational, and Photophysical Characterization of New Luminescent Dirhenium–Pyridazine Complexes Containing Bridging OR or SR Anions

Electrochemical Characterization and CO2 Reduction Reaction of a Family of Pyridazine-Bridged Dinuclear Mn(I) Carbonyl Complexes

Three recently synthesized neutral dinuclear carbonyl manganese complexes with the pyridazine bridging ligand, of general formula [Mn₂(μ-ER)₂(CO)₆(μ-pydz)] (pydz = pyridazine; E = O or S; R = methyl or phenyl), have been investigated by cyclic voltammetry in dimethylformamide and acetonitrile both under an inert argon atmosphere and in the presence of carbon dioxide. This family of Mn(I) compounds behaves interestingly at negative potentials in the presence of CO₂. Based on this behavior, which is herein discussed, a rather efficient catalytic mechanism for the CO₂ reduction reaction toward the generation of CO has been hypothesized.

Triarylamine-based hydrido-carboxylate rhenium(i) complexes as photosensitizers for dye-sensitized solar cells

We report dinuclear hydrido-carbonyl rhenium complexes employed in DSSCs for the first time. An improved performance in solar cell efficiency was achieved by molecular design.

Self-assembly of manganese(i) based thiolato bridged dinuclear metallacycles: synthesis, characterization, cytotoxicity evaluation and CO-releasing studies

Manganese(i) based thiolato bridged dinuclear metallacycles were assessed as anticancer agents along with myoglobin assay for CO-releasing studies.

Dirhenium Coordination Complex Endowed with an Intrinsically Chiral Helical-Shaped Diphosphine Oxide

A one-pot, multicomponent strategy was used to synthesize the first example of the dirhenium carbonyl coordination complex 2, in which the two metal atoms are connected through a chiral helical-shaped diphosphine oxide. Thanks to the flexibility of the helix of helicene 1, complex 2 was isolated in quite a good yield as a stable compound. It was characterized by analytical and spectroscopic techniques as well as by single-crystal X-ray analysis, which confirmed the chemical structure and the peculiar architecture of 2. In addition, computational studies were in agreement with the transitions observed in the experimental UV-vis spectrum, revealing the presence of two bands with maxima at about 520 (metal-to-ligand charge transfer) and 400 nm (IL).

The binuclear dual emitter [Br(CO)3Re(PN)(NP)Re(CO)3Br] (PN): 3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine, a new bridging P,N-bidentate ligand resulting from the ring opening of tetrahydrofuran

Lithium diphenylphosphide unexpectedly provokes the ring-opening of tetrahydrofuran (THF) and by reaction with 3,6-dichloropyridazine leads to the formation of the ligand 3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine (P⋯N), which was isolated. The reaction of this ligand with the (Re(CO)₃(THF)Br)₂ dimer yields the novel complex [Br(CO)₃Re(μ-3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine)₂Re(CO)₃Br] (BrRe(P⋯N)(N⋯P)ReBr), which was crystallized in the form of a chloroform solvate, (C₄₆H₄₀Br₂Cl₂N₄O₈P₂Re₂)·(CHCl₃). The monoclinic crystal (P2₁/n) displays a bimetallic cage structure with a symmetry inversion centre in the middle of the rhenium to rhenium line. The molecule shows two oxidation signals occurring at +1.50 V and +1.76 V which were assigned to the Re^I/Re^II and Re^II/Re^III metal-centered couples, respectively, while signals observed at -1.38 V and -1.68 V were assigned to ligand centered reductions. Experimental and DFT/TDDFT results indicate that the UV-Vis absorption maximum of BrRe(P⋯N)(N⋯P)ReBr occurring near 380 nm displays a metal to ligand charge transfer (MLCT) character, which is consistent with CV results. Upon excitation at this wavelength, a weak emission (Φ_em < 1 × 10^-3) is observed around 580 nm (in dichloromethane) which decays with two distinct lifetimes τ₁ and τ₂ of 24 and 4.7 ns, respectively. The prevalence of non-radiative deactivation pathways is consistent with efficient internal conversion induced by the high conformational flexibility of the P⋯N ligand's long carbon chain. Measurements in a frozen solvent at 77 K, where vibrational deactivation is hindered, show intense emission associated with the ³MLCT state. These results demonstrate that BrRe(P⋯N)(N⋯P)ReBr preserves the dual emitting nature previously reported for the mononuclear complex RePNBr, with emission associated with and states.

Dinuclear rhenium pyridazine complexes containing bridging chalcogenide anions: synthesis, characterization and computational study

Narrowing of the HOMO–LUMO gap on going down the chalcogen group makes the telluride derivative most promising for solar energy conversion.

New dinuclear hydrido-carbonyl rhenium complexes designed as photosensitizers in dye-sensitized solar cells

Dye-sensitized solar cells based on dinuclear hydrido-carbonyl rhenium complexes have been developed, achieving an overall solar conversion efficiency of 1.0%.

trans-Di-chlorido-bis-(pyridazine-κN)palladium(II)

The title compound, [PdCl₂(C₄H₄N₂)₂], contains two crystallographically unique complexes; the Pd^II atom lies on an inversion center in both cases. The two pyridazine units bonded to the Pd^II atom are thus coplanar although dihedral angles within each complex are different. In one complex, the angle between the ring plane and Pd—Cl bond is almost perpendicular [89.4 (1)°], while the other is tilted with an angle of 60.0 (1)°. In the crystal, weak C⋯H—N hydrogen bonds and C⋯H—Cl inter­actions connect the two independent complex mol­ecules.

Solid-state emission enhancement in vaulted trans-bis(salicylaldiminato)platinum(ii) crystals with halogen functionality

Chloro-substitution significantly increases the lower heat resistance of short-vaulted, non-substituted trans-bis(salicylaldiminato)Pt(ii) complex crystals, and maintains the intense emission of long-vaulted analogues, which leads to intense solid-state emission with low structural dependence.

Solid-state phosphorescence of trans-bis(salicylaldiminato)platinum(II) complexes bearing long alkyl chains: morphology control towards intense emission

Morphology control for intense solid-state phosphorescence of non-emissive, but potentially emissive crystals of platinum complexes and the mechanistic rationale are described. A series of trans-bis(salicylaldiminato)platinum(II) complexes bearing linear alkyl chains (1a: n=5; 1b: n=8; 1c: n=12; 1d: n=14; 1e: n=16; 1f: n=18) was synthesized and the solid-state emission properties were examined by using crystals/aggregates prepared under various precipitation conditions. Crystals of 1e, prepared using "kinetic" conditions including rapid cooling, high concentrations, and poor solvents, emit intensive yellow phosphorescence (λ(max)=545 nm) under UV irradiation at 298 K with an absolute quantum efficiency of 0.36, whereas all the crystals of 1a-1f prepared using "thermodynamic" conditions including slow cooling, low concentrations, and good solvents were either non- or less emissive with Φ(298K) values of 0.12 (1a), 0.11 (1b), 0.10 (1c), 0.07 (1d), 0.02 (1e), and 0.02 (1f) under the same measurement conditions. The amorphous solid 1e, prepared by rapid cooling and freeze-drying, was also non-emissive (Φ(298K)=0.02, 0.02). Temperature-dependent emission spectra showed that the kinetic crystals of 1e exhibit high heat-resistance towards emission decay with increasing temperature, whereas the amorphous solid 1e is entirely heat-quenchable. This is a rare example of the change from a non-emissive crystal into a highly emissive crystal by morphology control through crystal engineering. Emission spectra and powder X-ray diffraction (XRD) patterns of the emissive, kinetic crystals of 1e are clearly distinct from those of the less emissive, thermodynamic crystals of 1a-1f. Single-crystal XRD unequivocally establishes that the thermodynamic crystals of 1d have a multilayered lamellar structure supported by highly regulated, consecutive π-stacking interactions between imine moieties, whereas the kinetic crystals of 1e have a face-to-edge lamellar structure with less stacking. These results lead to the conclusion that 1) morphology control of long-chained complexes exclusively generates a metastable herringbone-based lamellar packing motif that exhibits intense emission and high heat-resistance, while 2) a thermodynamically stable, highly regulated, consecutive stacking motif is unfavorable for solid-state emission.