Effect of the back skeleton ligand on the ultrafast excited-state dynamics of Cu(I) cyano substituted bipyridine complexes

Cu(I) complexes have attracted a lot of research interest as potential alternatives to functional noble metal complexes. In previous research studies of the ultrafast dynamics of Cu(I) complexes, most of the acceptor ligands used are symmetric and examples of only a limited number of asymmetric ligands were reported. To further understand the ultrafast excited state dynamics of Cu(I) complexes with an asymmetric cyano-substituted bipyridine electron acceptor ligand, Cu(I) complexes with 6-cyano-2,2'-bipyridine and 4,4'-dimethyl-6-cyano-2,2'-bipyridine ligands in dichloromethane and acetonitrile were investigated by applying femtosecond time-resolved transient absorption (TA) spectroscopy. From the TA spectra, it was found that two different metal-to-ligand charge transfer (MLCT) states with different nature could be populated after pseudo-Jahn-Teller distortion. Time-dependent density functional theory (TD-DFT) calculation results also support the hypothesis that, in one MLCT state, the electron density is donated from the Cu(I) center to the cyanobipyridine ligand with electron density delocalised on the whole bipyridine ligand and in the other MLCT state the electron density is donated from the Cu(I) center to the cyano-substituted pyridine fragment of the cyanobipyridine ligand. This result indicates that asymmetric electron acceptors may lead to the population of extra excited states compared with symmetric electron acceptors.

Realizing Color Transitions for Three Copper (I) Cluster Organic-Inorganic Hybrid Materials by Adjusting Reaction Conditions

Copper iodide organic-inorganic hybrid materials have been favored by many researchers in the field of solid-state lighting (SSL) due to their structural diversity and optical adjustability. In this paper, three isomeric copper iodide cluster hybrid materials, Cu4I6(L)2(1), Cu5I4.5Cl2.5(L)2(2) and Cu5I7(L)2) (3) (L=1-(4-methylpyrimidin-2-yl)-1,4-diazabicyclo[2.2.2]octan-1-ium), were achieved by adjusting the reaction conditions. The crystal color transit from green, yellow to orange and the internal quantum yield (IQY) increase from 57 %-88 %. All three complexes have good thermal stability, good solution processability, and high quantum yield. And origin and mechanism of luminescence of complexes were further studied. This study can provide ideas and theoretical basis for the regulation of cuprous iodide cluster luminescent materials.

Photoactive Copper Complexes: Properties and Applications

Photocatalyzed and photosensitized chemical processes have seen growing interest recently and have become among the most active areas of chemical research, notably due to their applications in fields such as medicine, chemical synthesis, material science or environmental chemistry. Among all homogeneous catalytic systems reported to date, photoactive copper(I) complexes have been shown to be especially attractive, not only as alternative to noble metal complexes, and have been extensively studied and utilized recently. They are at the core of this review article which is divided into two main sections. The first one focuses on an exhaustive and comprehensive overview of the structural, photophysical and electrochemical properties of mononuclear copper(I) complexes, typical examples highlighting the most critical structural parameters and their impact on the properties being presented to enlighten future design of photoactive copper(I) complexes. The second section is devoted to their main areas of application (photoredox catalysis of organic reactions and polymerization, hydrogen production, photoreduction of carbon dioxide and dye-sensitized solar cells), illustrating their progression from early systems to the current state-of-the-art and showcasing how some limitations of photoactive copper(I) complexes can be overcome with their high versatility.

The Tail Wags the Dog: The Far Periphery of the Coordination Environment Manipulates the Photophysical Properties of Heteroleptic Cu(I) Complexes

In this work we show, using the example of a series of [Cu(Xantphos)(N^N)]+ complexes (N^N being substituted 5-phenyl-bipyridine) with different peripheral N^N ligands, that substituents distant from the main action zone can have a significant effect on the physicochemical properties of the system. By using the C≡C bond on the periphery of the coordination environment, three hybrid molecular systems with -Si(CH3)3, -Au(PR3), and -C2HN3(CH2)C10H7 fragments were produced. The Cu(I) complexes thus obtained demonstrate complicated emission behaviour, which was investigated by spectroscopic, electrochemical, and computational methods in order to understand the mechanism of energy transfer. It was found that the -Si(CH3)3 fragment connected to the peripheral C≡C bond changes luminescence to long-lived intra-ligand phosphorescence, in contrast to MLCT phosphorescence or TADF. The obtained results can be used for the design of new materials based on Cu(I) complexes with controlled optoelectronic properties on the molecular level, as well as for the production of hybrid systems.