Synthesis and Characterization of Redox-Active Mononuclear Fe(κ2-dppe)(η5-C5Me5)-Terminated π-Conjugated Wires

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure-Property Relationships and Applications

Conjugated poly-ynes and poly(metalla-ynes) constitute an important class of new materials with potential application in various domains of science. The key factors responsible for the diverse usage of these materials is their intriguing and tunable chemical and photophysical properties. This review highlights fascinating advances made in the field of conjugated organic poly-ynes and poly(metalla-ynes) incorporating group 4-11 metals. This includes several important aspects of conjugated poly-ynes viz. synthetic protocols, bonding, electronic structure, nature of luminescence, structure-property relationships, diverse applications, and concluding remarks. Furthermore, we delineated the future directions and challenges in this particular area of research.

A Redox-Switchable Germylene and its Ligating Properties in Selected Transition Metal Complexes

The synthesis, structure, and full characterization of a redox-switchable germylene based on a [3]ferrocenophane ligand arrangement, [Fc(NMes)₂ Ge] (4), is presented. The mesityl (Mes)-substituted title compound is readily available from Fc(NHMes)₂ (2) and Ge{N(SiMe₃ )₂ }₂ , or from the dilithiated, highly air- and moisture-sensitive compound Fc(NLiMes)₂ ⋅3 Et₂ O (3) and GeCl₂ . Cyclic voltammetry studies are provided for 4, confirming the above-mentioned view of a redox-switchable germylene metalloligand. Although several 1:1 Rh^I and Ir^I complexes of 4 (5-7) are cleanly formed in solution, all attempts to isolate them in pure form failed due to stability problems. However, crystalline solids of [Mo(κ¹ Ge-4)₂ (CO)₄ ] (8) and [W(κ¹ Ge-4)₂ (CO)₄ ] (9) were isolated and fully characterized by common spectroscopic techniques (8 by X-ray diffraction). DFT calculations were performed on a series of model compounds to elucidate a conceivable interplay between the metal atoms in neutral and cationic bimetallic complexes of the type [Rh(κ¹ E-qE)(CO)₂ Cl]^0/+ (qE=[Fc(NPh)₂ E] with E=C, Si, Ge). The bonding characteristics of the coordinated Fc-based metalloligands (qE/qE⁺ ) are strongly affected upon in silico oxidation of the calculated complexes. The calculated Tolman electronic parameter (TEP) significantly increases by approximately 20 cm^-1 (E=C) to 25 cm^-1 (E=Si, Ge) upon oxidation. The change in the ligand-donating abilities upon oxidation can mainly be attributed to Coulombic effects, whereas an orbital-based interaction appears to have only a minor influence.

Fe(dppe)(η5-C5Me5)-Based Phenylalkynyl Complexes Featuring an NO2 End Group: A Theoretical Analysis

Electronic structures and optical properties of a series of compounds Fe(dppe)(η5-C5Me5){[C≡C(1,4-C6H4)]nNO2} (1–3; n = 1–3, dppe = 1,2-bis(diphenylphosphino)ethane) were investigated with the aid of density functional theory and time-dependent density functional theory computations. The results reveal that the extension of the carbon-rich chain has a moderate influence on the electronic properties of the studied compounds in their ground state, but affects notably their spectroscopic properties, with some unexpected hypsochromic shift of the lower energy absorption bands upon carbon chain lengthening. The appropriate excitations responsible for the low-energy absorption bands involve mainly HOMO–LUMO transitions dominated by important metal-to-ligand charge transfer. A functional including long-range corrections is necessary to reproduce the experimental results.

Accurate yet feasible computations of resonance Raman spectra for metal complexes in solution: [Ru(bpy)3](2+) as a case study

Herein we present a new and promising approach for the high-resolution modeling of vibrational resonance Raman spectra of metal complexes in solution. The model explicitly includes Duschinsky couplings, solvent effects, and anharmonic corrections in a computational tool able to treat large molecular systems containing transition metals.