Synthesis, characterization, and DFT study of novel metallo phtalocyanines with four carboranyl clusters as photosensitisers for the photodynamic therapy of breast cancer cells.

The synthesis and characterization of novel Zn(II) and Co(II) phthalocyanines 4 and 5, respectively containing four o-carboranyl units (40 boron atoms, 32.5% boron by weight) at the peripheral positions are described. The phthalocyanines (Pcs) were synthesized by cyclotetramerization of the previously prepared precursor 4­(2­thiol­o­carboranyl)thiolato­phthalonitrile 3 with the presence of metal salt in boiling dry DMF under a dry nitrogen atmosphere. They were characterized by elemental analysis, UV-Vis, FT-IR, MALDI-TOF mass and 1H NMR spectrometry. To elucidate the structural, spectroscopic and bonding properties of the obtained compounds, calculations with DFT/TD-DFT(Density Functional Theory/Time Dependent-Density Functional Theory) were performed. The cytotoxic effects of 4 and 5 on cancer cells and epithelial cells were determined. The targeted cytotoxicities of both compounds against cancer cells were analyzed with the cell viability test. Although, 4 caused less PDT (Photodynamic therapy) based decrease in cell viability of cancer cell line in comparison to 5, it showed comparatively high cytotoxicity against cancer cells but not epithelial cells. The IC50 (half maximal inhibitory concentration) values indicate that 4 with PDT shows 17.3 fold more cytotoxicity to breast cancer cells than epithelial cells. The selectivity in cytotoxicity of 4 makes it a good candidate for cancer treatment. Interestingly, 5 was found to be highly cytotoxic for both cancer and epithelial cell lines. Considerably, 5 might be used as a cancer drug when combined with targeting agents such as antibodies and aptamers.

Computational studies of metal carbonyl complexes of 3[4-ethyl(phenly)imino][indoline-2-one] and 3[4-butyl(phenly)imino][indoline-2-one].

Use and application of Schiff bases are extended to many different fields of technology. (ISE)M(CO)5 complex [M = Cr (1), Mo (2), W (3), and where ISE is 3[4-ethyl(phenly)imino][indoline-2-one]; and (ISB)M(CO)5 [M = Cr (4), Mo (5), W (6)], where ISB is 3[4-butly(phenly)imino][indoline-2-one] were investigated by computational methods. Computations were carried out using density functional theory (DFT) with B3LYP and CAM-B3LYP functionals, in conjunction with LanL2DZ basis set for metals and cc-PVTZ basis set for other atoms. Time-dependent density functional theory (TDDFT) was used at the same level to obtain the electronic transitions. Molecular orbital energies, UV-Vis spectra, and total electron densities of investigated molecules were shown in the gas phase and in THF. Metal complexes showed higher absorption coefficients compared to ISE and ISB in the visible region. Additionally, they displayed absorption peaks at longer wavelengths and full MLCT character in solution, and W complexes required less energy compared to the complexes of other investigated metal ions. Among the investigated systems, (ISE)W(CO)5 and (ISB)W(CO)5 complexes with lowest HOMO-LUMO gaps are found to be the best candidates for photosensitive material production. Graphical Abstract UV-Vis absorption spectra of ISE and (ISE)W(CO)5.

Syntheses and studies of electron/energy transfer of new dyads based on an unsymmetrical perylene diimide incorporating chelating 1,10-phenanthroline and its corresponding square-planar complexes with dichloroplatinum(ii) and dichloropalladium(ii ).

Perylene diimides (PDIs) are among the most versatile and functional dyes for supramolecular structures displaying characteristic high absorptions and photo-luminescence properties as the prerequisite for optoelectronic thin film devices. Despite intense investigations into these semi-conducting and electro-active materials, details of their electronic structure are still under examination. In particular, non-planar twisted PDIs as an electron acceptor is a promising model system for efficient charge generation and transport processes. Therefore, a new dyad, an unsymmetrical PDI, N'-(2-ethylhexyl)-N'-(1,10-phenanthroline)-1,6,7,12-tetrakis-(4-methoxyphenoxy)-3,4,9,10-tetracarboxylic acid diimide (1) and its corresponding dichloroplatinum(ii) and dichloropalladium(ii) complexes as new dyads, [(Cl2)M(ii)-(1)] where, M(ii) = Pt(ii) (2) and Pd(ii) (3), were prepared. These dyads were fully characterized by FT-IR, 1D-NMR (1H-NMR and 13C-NMR), 2D-NMR (1H-1H COSY, 1H-13C HSQC, 1H-13C HMBC), MALDI TOF mass and UV-Vis spectroscopy. Electronic structure calculations have been employed based on Time-Dependent Density Functional Theory (TDDFT) calculations for the geometry-optimized electronic ground state structures in the gas phase and in dichloromethane (DCM). Current results indicate that 2 and 3 have similar HOMO-LUMO energy gaps which are smaller than 1. The energy and charge transfer processes with molecular structures are crucial for the design of future functional dyads based on donor and acceptor moieties for hybrid optoelectronic devices. Charge transfer mechanisms were also investigated with linear absorption, fluorescence and ultrafast transient absorption spectra for the newly synthesized compounds in DCM. The observed ultrafast intramolecular charge transfer from donor units on the PDI-2 compound is related to fluorescence quenching and faster singlet decay on transient measurements.

DFT and TDDFT investigation of the Schiff base formed by tacrine and saccharin.

Schiff bases have many chemical and biological applications in medicine and pharmaceuticals due to the presence of an imine group (-C=N-). These bases are used in many different fields of technology, and in photochemistry because of their photochromic properties. Here, the structural and electronic properties of the Schiff base formed by tacrine and saccharin (TacSac) were explored using density functional theory with the B3LYP, M06-2X, M06L, and ωB97XD functionals in combination with the 6-311++G(d,p) basis set. The time-dependent formalism was used at the B3LYP/6-311++G(d,p) level to obtain electronic transitions. The calculations were repeated in an implicit solvent model mimicking water, using the polarizable continuum model in conjunction with a solvation model based on a density approach. The results indicate that TacSac cannot form spontaneously, but can be obtained in mild reactions. However, the resulting Schiff base displays different characteristics to its monomers. It also has the potential for use in photochemical intramolecular charge-transfer systems. Graphical Abstract Intramolecular charge transfer between HOMO and LUMO of TacSac.

Solvatochromism of pyranine-derived photoacids.

Photoacidity is frequently found in aromatic alcohols where the equilibrium dissociation constant increases by some orders of magnitude upon electronic excitation. In this study we investigated the solvatochromism of a family of recently synthesized super-photoacids and their methylated counterparts based on pyrene. The chemical similarity of these molecules on the one hand and their differing photoacidity with pKa* values between -0.8 and -3.9 on the other allow for gaining insights into the mechanisms contributing to excited-state proton transfer. Three different solvent scales, namely Lippert-Mataga, Kamlet-Taft and Catalán, were independently employed in this study and gave consistent results. We found the strongest correlation of the excited-state acidity with the dipolarity of the excited state, pem ranging from -1775 cm(-1) to -2500 cm(-1), and a concomitant change in the permanent dipole moment of roughly 14 Debye. Spectral changes due to varying basicity of the solvent, which probes the conjugated property of the solute, are found to be less indicative of the graduation of excited-state acidity, i.e. bem values between -700 and -1200 cm(-1). The solvent acidity is the only parameter with a distinct influence on the electronic spectra of the deprotonated species. The low values of aem ~ 400 cm(-1), which are 3-4× smaller than aabs and aexc, indicate the low basicity of these species in the excited state. Triggered by semiempirical theoretical calculations, the energetic splitting between the two lowest excited states could be related to the excited-state acidity and points to alterations in the electronic mixing of locally excited and charge-transfer states, caused by the substituents. Differences between the threefold negatively charged pyranine and the new neutral photoacids are also discussed.