Temperature-sensitive emission of dialkylaminostyrylhetarene dyes and their incorporation into phospholipid aggregates: Applicability for thermal sensing and cellular uptake behavior.

A series of dialkylaminostyrylhetarene dyes constructed from electron-rich and electron-deficient moieties of various structures connected via vinylene π-bridges are introduced as temperature-sensitive luminophores. The temperature dependent emission of the dyes in the acidified dichloromethane solutions derives from temperature-induced shift of the equilibrium between neutral and protonated forms of the dyes. The heating-induced blue shift and intensification of emission of neutral form of the dyes make them a promising basis for development of nanoparticles exhibiting temperature-sensitivity in aqueous solutions at pH typical of biological liquids. Hydrophobicity-driven incorporation of the water insoluble dyes into L-α-phosphatidylcholine(PC)-based bilayers allows to obtain water dispersible dye-PC aggregates, and to follow their emission in the aqueous solutions. Structure of the dyes has strong impact on the efficacy of the dyes incorporation into the PC-based bilayers, temperature sensitivity of emission of the dye-PC aggregates and its reversibility under the heating/cooling cycles. This enables structural optimization of the dyes in order to obtain the dye-PC species demonstrating maximal temperature dependence and reversibility of their luminescence in aqueous solutions. The selected leader exhibits low cytotoxicity exemplified for M-HeLa and Chang Liver cell lines, while the efficient cell internalization of the dye, manifested in the staining of the cell cytoplasm, opens further opportunities for biosensing applications.

Novel quinoxalinone-based push-pull chromophores with highly sensitive emission and absorption properties towards small structural modifications.

The photophysical properties of a series of novel push-pull quinoxalinone-based chromophores that strongly absorb and emit light in the broad visible spectrum were comprehensively studied both experimentally and through quantum chemical methods. The drastic influence of the position of the electron-donor dimethylaminostyryl (DMAS) in the quinoxalinone core on its absorption and emission intensities as well as on the solvatochromic behavior of the concerned isomers has been established. No dependence of the photophysical properties of the chromophores on the conformation of the DMAS group was found. Quantum chemical computations provided a reliable theoretical rationalization of the observed spectral features, in particular, the important one related to Stokes shift. The local or intramolecular charge-transfer (ICT) character of the key electronic transitions has been assessed using a quantitative natural transition orbitals analysis and based on the novel topological descriptors of the electronic density rearrangement. This study shows that the ICT effects are not the primary factors contributing to the drastic difference in the emission efficiency of push-pull chromophores that are structurally very similar.

The first representatives of tetranuclear gold(i) complexes of P,N-containing cyclophanes.

The first representatives of the tetranuclear gold(i) complexes of P,N-containing cyclophanes with two 1,5-diaza-3,7-diphosphacyclooctane rings incorporated into the macrocyclic core have been obtained. The complexation leads to a change in ligand conformations so that the diazadiphosphacyclooctane fragments of the complexes adopt twist-chair conformations, and two of the four gold(i) ions are located over and under the partially collapsed macrocyclic cavity. The complexes demonstrate moderate solid-state green emission.

Synthesis of novel pyridyl containing phospholanes and their polynuclear luminescent copper(i) complexes.

A novel type of cyclic P,N-ligands, pyridyl containing phospholanes, has been synthesized in a moderate yield by the reaction of primary phosphines with 1,4-dichlorobutane in a superbasic medium. A series of homo tetranuclear octahedral Cu4I4L2, dinuclear tetrahedral Cu2I2L3, and dinuclear "head-to-tail" Cu2I2L2 luminescent complexes with these ligands were obtained. All the compounds were characterized using a range of spectroscopic and computational techniques, and in the case of some Cu4I4L2 and Cu2I2L3 complexes, by single crystal X-ray diffraction. The structural diversity of the obtained complexes was reflected in their photophysical properties: phosphorescence spectra of the compounds display emission in broad spectral range of 471-615 nm. TD-DFT computations allow the assignment of a single emission band around 550 nm for Cu2I2L3 complexes and 471 nm for Cu2I2L2 complex to a vertical triplet-singlet transition from a metal-to-ligand and halide-to-ligand charge-transfer (3)(M + X)LCT excited state, whereas a second band at around 600 nm in the spectra of octahedral Cu4I4L2 complexes was assigned predominantly to Cu4I4 cluster-centered ((3)CC) excited state.