Tetra- and hexanuclear copper(I) iminothiolate complexes: synthesis, structures, and solid-state thermochromic dual emission in visible and near-infrared regions

Unraveling the Remarkable Influence of Substituents on the Emission Variation and Circularly Polarized Luminescence of Dinuclear Aluminum Triple-Stranded Helicates

This study explored the development of functional dyes using aluminum, focusing on aluminum-based dinuclear triple-stranded helicates, and examined the effects of substituent variations on their structural and optical properties. Key findings revealed that the modification of methyl groups to the pyrrole positions significantly extended the conjugation system, resulting in a red shift in the absorption and emission spectra. Conversely, the modification of methyl groups at the methine positions due to steric hindrances increased the torsion angle of the ligands, leading to a blue shift in the absorption and emission spectra. A common feature across all complexes was that in the excited state, one of the three ligands underwent significant structural relaxation. This led to a pronounced Stokes shift and minimal spectra overlap with high photoluminescence behaviors. Moreover, our research extended to the optical resolution of the newly synthesized complexes by analyzing the chiroptical properties of the resulting enantiomers, including their circular dichroism and circularly polarized luminescence. These insights offer valuable contributions to the design and application of novel aluminum-based functional dyes, potentially influencing a range of fields, from materials science to optoelectronics.

Novel Cu(I)-5-nitropyridine-2-thiol Cluster with NIR Emission: Structural and Photophysical Characterization

A novel Cu(I) cluster compound has been synthesized by reacting CuI with the 2,2'-dithiobis(5-nitropyridine) ligand under solvothermal conditions. During the reaction, the original ligand breaks into the 5-nitropyridine-2-thiolate moiety, which acts as the coordinating ligand with both N- and S-sites, leading to a distorted octahedral Cu₆S₆ cluster. The structure has been determined by single-crystal X-ray diffraction and FT-IR analysis, and the photophysical properties have been determined in the solid state by means of steady-state and time-resolved optical techniques. The cluster presents a near-infrared emission showing an unusual temperature dependence: when passing from 77 to 298 K, a blue-shift of the emission band is observed, associated with a decrease in its intensity. Time-dependent-density functional theory calculations suggest that the observed behavior can be ascribed to a complex interplay of excited states, basically in the triplet manifold.

Solid-State Structures and Photoluminescence of Lamellar Architectures of Cu(I) and Ag(I) Paddlewheel Clusters with Hydrogen-Bonded Polar Guests

Two hexanuclear paddlewheel-like clusters appending six carboxylic-acid pendants have been isolated with the inclusion of polar solvent guests: [Cu₆(Hmna)₆]·7DMF (1·7DMF) and [Ag₆(Hmna)₆]·8DMSO (2·8DMSO), where H₂mna = 2-mercaptonicotininc acid, DMF = N,N’-dimethylformamide, and DMSO = dimethyl sulfoxide. The solvated clusters, together with their fully desolvated forms 1 and 2, have been characterized by FTIR, UV–Vis diffuse reflectance spectroscopy, TG-DTA analysis, and DFT calculations. Crystal structures of two solvated clusters 1·7DMF and 2·8DMSO have been unambiguously determined by single-crystal X-ray diffraction analysis. Six carboxylic groups appended on the clusters trap solvent guests, DMF or DMSO, through H-bonds. As a result, alternately stacked lamellar architectures comprising of a paddlewheel cluster layer and H-bonded solvent layer are formed. Upon UV illumination (λ_ex = 365 nm), the solvated hexasilver(I) cluster 2·8DMSO gives intense greenish-yellow photoluminescence in the solid state (λ_PL = 545 nm, Φ_PL = 0.17 at 298 K), whereas the solvated hexacopper(I) cluster 1·7DMF displays PL in the near-IR region (λ_PL = 765 nm, Φ_PL = 0.38 at 298 K). Upon complete desolvation, a substantial bleach in the PL intensity (Φ_PL < 0.01) is observed. The desorption–sorption response was studied by the solid-state PL spectroscopy. Non-covalent interactions in the crystal including intermolecular H-bonds, CH⋯π interactions, and π⋯π stack were found to play decisive roles in the creation of the lamellar architectures, small-molecule trap-and-release behavior, and guest-induced luminescence enhancement.