Luminescence Solvato- and Vapochromism of Alkynyl-Phosphine Copper Clusters

The reaction of [Cu(NCMe)4][PF6] with aromatic acetylenes HC2R and triphosphine 1,1,1-tris(diphenylphosphino)methane in the presence of NEt3 results in the formation of hexanuclear Cu(I) clusters with the general formula [Cu6(C2R)4{(PPh2)3CH}2][PF6]2 (R = 4-X-C6H4 (1-5) and C5H4N (6); X = NMe2 (1), OMe (2), H (3), Ph (4), CF3 (5)). The structural motif of the complexes studied consists of a Cu6 metal core supported by two phosphine ligands and stabilized by σ- and π-coordination of the alkynyl fragments (together with coordination of pyridine nitrogen atoms in cluster 6). The solid state structures of complexes 2-6 were determined by single crystal XRD analysis. The structures of the complexes in solution were elucidated by (1)H, (31)P, (1)H-(1)H COSY NMR spectroscopy, and ESI mass spectrometry. Clusters 1-6 exhibit moderately strong phosphorescence in the solid state with quantum yields up to 17%. Complexes 1-5 were found to form solvates (acetone, acetonitrile) in the solid state. The coordination of loosely bound solvent molecules strongly affects emission characteristics and leads to solvato- and vapochromic behavior of the clusters. Thus, solvent-free and acetonitrile solvated forms of 3 demonstrate contrasting emission in orange (615 nm) and blue (475 nm) regions, respectively. The computational studies show that alkynyl-centered IL transitions mixed with those of MLCT between the Cu6 metal core and the ligand environment play a dominant role in the formation of excited states and can be considerably modulated by weakly coordinating solvent molecules leading to luminescence vapochromism.This research has been supported by St. Petersburg State University Research Grant 0.37.169.2014, and Russian Foundation for Basic Research Grants 13-03-00970, 14-03-32077, and 13-03-12411. Academy of Finland (Grant 268993/2013, I.O.K), University of Eastern Finland (strategic funding—Russian–Finnish collaborative project), is also gratefully acknowledged. The work was carried out using equipment of the Analytical Center of Nano- and Biotechnologies of SPbSPU with financial support of the Ministry of Education and Science of Russian Federation; Centers for Magnetic Resonance, X-ray Diffraction Studies, Chemical Analysis and Materials Research, Optical and Laser Materials Research; and Computer Center of St. Petersburg State University

Non-covalent intramolecular interactions through ligand-design promoting efficient photoluminescence from transition metal complexes

Ligand design allows arranging ligand entities and functional groups in order to generate a plethora of non-covalent interactions such as pi stacking, H bridging, and Lewis acid-base interactions in the second coordination sphere of transition metal complexes and thus modulate the photophysical properties. In addition to these forces, steric strain and ligand entanglement can lead to massive restrictions in the molecular geometry of complexes and in consequence to high rigidity and thus high geometrical similarity of the complexes electronic ground and excited states. This similarity is one of the prerequisites for efficient photoluminescence of such complexes since it hampers the unwanted radiationless decay from the excited states. Compared with other strategies to design efficient triplet emitting complexes, the approach of intramolecular non-covalent interaction has only recently entered the stage and has thus a lot of potential. In this review we will trace this approach presenting illustrative and recent examples for suitable ligand design. (C) 2019 Elsevier B.V. All rights reserved

Activation of the Cyano Group at Imidazole via Copper Stimulated Alcoholysis

Reactions of 4,5-dicyano-1-methylimidazole with CuX2 (X = Cl, Br) in alcohol solvents (ethanol and methanol) resulted in the formation of Cu(II) carboximidate complexes [CuCl2(5- cyano-4-C(OEt)N-1-methylimidazole)(EtOH)] (1), [Cu2(µ-Cl)2Cl2(5-cyano-4-C(OMe)N-1-methylimidazole)2] (2), [Cu2(µ-Br)2Br2(5-cyano-4-C(OMe)N-1-methylimidazole)2] (3), and [Cu2(µ-Br)2Br2(5-cyano-4-C(OEt)N-1-methylimidazole)2] (4). The structures were determined by the X-ray crystallographic method, and further spectroscopic and computational methods were employed to explain the structural features. The solvent contributed to the alcoholysis reaction of the cyano group, as the result of which the ligand coordinated to the metal center in bidentate mode forming a five-membered chelating ring. In 1, the solvent also acts as an additional ligand, which coordinates to the metal center of a monomeric complex. In compounds 2–4, two halogen ligands link the metal atoms forming dihalo-bridged copper dimers. The infrared absorption characteristics were verified by simulation of the infrared spectra at the density functional theory level. In addition, the electronic absorption characteristics were explained by simulation of the UV–Vis spectra using the TD-DFT method. Molecular modelling at the DFT level was performed to study the effects of halogen type and steric hindrance of the alkoxy groups in forming the copper(II) complexes.peerReviewe

Synthesis, structural characterization, photophysical properties and theoretical analysis of gold(I) thiolate-phosphine complexes

11 páginas, 9 figuras, 2 tablas, 2 esquemas.-- et al.A series of luminescent dinuclear neutral complexes of stoichiometry [(AuSPh)2(PPh2-(C6H4)n-PPh2)] (n = 1, 2, 3) as well as their tetranuclear cationic derivatives [(Au2SPh)2(PPh2-(C6H4)n-PPh2)2](PF6)2 are reported. Their crystal structures have been elucidated by X-ray studies. These studies indicate that, for the dinuclear species, only when n = 1 the molecules exhibit intermolecular aurophilic interactions. None of the tetranuclear species crystallizes in their molecular form, due to the formation of aggregates through Au***Au interactions. The origin of the luminescence has been analyzed by computational studies indicating that the presence or absence of aurophilic interactions does not affect the luminescent behavior and that intraligand charge transfer processes which involve the thiolate and the diphosphine are responsible for the emissions. The result is in contrast with the thiolate–gold charge transfer processes which dominate the photophysics of gold-thiolate compounds and reveals the influence of the phenylene spacers in the emissive behavior of these compounds.Financial support fromthe Academy of Finland (I.O.K.),Russian Foundation for Basic Research (grants 09-03-12309-CSIC-a and 09-03-12309) is gratefully acknowledged. We also thank the Dirección General de Investigación Científica y T´ecnica (CTQ2007- 67273-C02-01), the CSIC/Russian Foundation for BasicResearch (RFBR) (N 2008RU0065) for financial support and to the Supercomputing Center of Galicia (CESGA-CSIC) for providing Access to the FINIS TERRAE System.Peer reviewe

Solvent directs the dimensionality of Cu-dicyanoimidazoles

In this paper, we report one-pot reactions of the same reactants 4,5-dicyanoimidazole and CuI in different solvents. In pure MeCN, the reaction resulted in previously reported MOF structure [Cu(4,5-dicyanoimidazole)]n.(MeCN)0.5n (1). On the other hand, when MeCN/MeOH solvent mixture was used, a new coordination polymer [Cu(4,5-dicyanoimidazole)(MeCN)(CuI)]n (2) was formed. The crystallization yielded very different structures as determined by X-ray crystallography. In 1, the solvent molecule acetonitrile occupies the MOF pores via weak interactions, but in 2 it is coordinated to the metal center. Computational DFT calculations and topological charge density analysis were utilized to explore the different crystal structures with the focus on the role of the methanol solvent.peerReviewe