Targeted Synthesis of NIR Luminescent Rhenium Diimine cis,trans-[Re( NN )(CO)2 (L)2 ]n+ Complexes Containing N-Donor Axial Ligands: Photophysical, Electrochemical, and Theoretical Studies.

The combined action of ultraviolet irradiation and microwave heating onto acetonitrile solution of [Re( NN )(CO)3 (NCMe)]OTf ( NN =phenantroline and neocuproine) afforded cis,trans-Re( NN )(CO)2 (NCMe)2 ]+ acetonitrile derivatives. Substitution of relatively labile NCMe with a series of aromatic N-donor ligands (pyridine, pyrazine, 4,4'-bipyridine, N-methyl-4,4'-bipyridine) gave a novel family of the diimine cis,trans-[Re( NN )(CO)2 (L)2 ]+ complexes. Photophysical studies of the obtained compounds in solution revealed unusually high absorption across the visible region and NIR phosphorescence with emission band maxima ranging from 711 to 805 nm. The nature of emissive excited states was studied using DFT calculations to show dominant contribution of 3 MLCT (dπ(Re)→π*( NN )) character. Electrochemical (CV and DPV) studies of the monocationic diimine complexes revealed one reduction and one oxidation wave assigned to reduction of the diimine moiety and oxidation of the rhenium center, respectively.

Luminescent Complexes of the Trinuclear Silver(I) and Copper(I) Pyrazolates Supported with Bis(diphenylphosphino)methane.

The first example of trinuclear copper(I) and silver(I) pyrazolates adducts with a tertiary diphosphine (Ph2PCH2PPh2) retaining trimeric [MPz]3 core is reported. Despite rather strong M-P bonding, the complexes are able to undergo the dissociation of one M-P bond leading to the "merry-go-round" movement of P atoms over the M3 triangle. The copper complex displays emission from 1MLCT and 3MLCT states. The triplet and singlet states are separated by a relatively small energy gap (1080 cm-1) that triggers the thermally activated delayed fluorescence (TADF) behavior and leads to the worthy quantum yield of 41% at 298 K. The silver complex in the solid state and frozen solution shows dual emission originating from the 1IL and 3MLCT states that is dictated by the much higher energy difference between the emissive singlet and triplet as well as by the essentially different nature of these states.

Self-assemble nanoparticles based on polypeptides containing C-terminal luminescent Pt-cysteine complex.

The growing attention to the luminescent nanocarriers is strongly stimulated by their potential application as drug delivery systems and by the necessity to monitor their distribution in cells and tissues. In this communication we report on the synthesis of amphiphilic polypeptides bearing C-terminal phosphorescent label together with preparation of nanoparticles using the polypeptides obtained. The approach suggested is based on a unique and highly technological process where the new phosphorescent Pt-cysteine complex serves as initiator of the ring-opening polymerization of α-amino acid N-carboxyanhydrides to obtain the polypeptides bearing intact the platinum chromophore covalently bound to the polymer chain. It was established that the luminescent label retains unchanged its emission characteristics not only in the polypeptides but also in more complicated nanoaggregates such as the polymer derived amphiphilic block-copolymers and self-assembled nanoparticles. The phosphorescent nanoparticles display no cytotoxicity and hemolytic activity in the tested range of concentrations and easily internalize into living cells that makes possible in vivo cell visualization, including prospective application in time resolved imaging and drug delivery monitoring.