Facile Synthesis of Ambient Stable Pyreno[4,5-b]pyrrole Monoanion and Pyreno[4,5-b:9,10-b’]dipyrrole Dianion: From Serendipity to Design

The stability of single or multiple negatively charged π-conjugated organic compounds is greatly influenced by its electronic delocalization. Herein, we report a strategic methodology for isolation of a mysterious compound....

Bandgap tunability from synergistic mixture of Pandanus amaryllifolius and Curcuma longa as photo-absorber candidates

The application of natural plant-derived dyes to replace ruthenium-based material as photo-absorber in solar cells application, have been extensively studied. Several advantages such as low cost, abundant in supply, sustainability and environmentally-safe make natural materials as current favourite photo-absorber. Natural plant-derived dyes are known containing natural compounds (e.g. carotenoids, chlorophylls, anthocyanins) that have the characteristics of electronic delocalization in extended ?-orbital system involving in electronic transfer mechanism. To date, massive investigations were done to exploit this system to be used as a potential photo-absorber in solar cells. Due to this matter, the hybrid dyes from the mixture of Pandanus amaryllifolius (pandan, P) and Curcuma longa (turmeric, T) were successfully prepared and several physical characterizations were carried out to analyse the photo-absorber (sensitizer) properties. From the results obtained, the ratios of P:T was varied into 1:2, 1:4, 4:1, and 8:1. This ratio has changed the wavelength of absorbers that were slightly shifted and the indirect bandgap (Eg) also were significantly changed. With this new approach, the bandgap of the hybrid dyes as core point in modulating electrical conductivity of photo-absorber can be simply tuned. By implying two different extract dyes to form hybrid dyes, the bandgap was found decreased with higher ratio of T used. Overall results suggesting that by adjusting the ratio of hybrid dyes, the photo-absorber properties and the Eg values were differed and with slightly modification, better electrical conductivity can be expected for solar cells application.

Synthesis of a Ru(II) Complex with a Naphthoquinone-Annelated Imidazole Ligand Exhibiting Proton-Responsive Redox and Luminescent Behavior

A mononuclear ruthenium complex, [RuII(L)(bpy)2](PF6), with a naphthoquinone-annelated imidazole ligand HL (2-(pyridin-2-yl)-1H-naphtho[2,3-d]imidazole-4,9-dione) was synthesized and structurally characterized. Electrochemical study reveals that the Ru complex shows four reversible redox waves at +0.98 V, −1.13 V, −1.53 V, and −1.71 V versus SCE in acetonitrile, which are assigned to Ru(II)/Ru(III), L−/L•2−, and two bpy/bpy•− redox couples, respectively. The redox potential of Ru(II)/Ru(III) was positively shifted upon the addition of trifluoromethanesulfonic acid due to protonation of the L− moiety, leading to stabilization of the Ru 4d orbital. In UV-vis absorption measurements for the Ru complex in acetonitrile, a metal-to-ligand charge transfer (MLCT) band was observed at 476 nm, which was shifted to 450 nm by protonation, which might be due to a decrease in the electron delocalization and stabilization of the π orbitals in L−. The blue shift of the MLCT band by protonation was associated with a shift of an emission band from 774 nm to 620 nm, which could be caused by the decreased electronic delocalization in the MLCT excited state. These electrochemical and spectroscopic changes were reversible for the protonation/deprotonation stimuli.

Chemical and Biological Evaluation of Thiosemicarbazone-Bearing Heterocyclic Metal Complexes

: Thiosemicarbazones (TSCNs) constitute a broad family of compounds (R1R2C=N-NH-C(S)-NR3R4) particularly attractive because many of them display some biological activity against a wide range of microorganisms and cancer cells. Their activity can be related with their electronic and structural properties, which offer a rich set of donor atoms for metal coordination and a high electronic delocalization providing different binding modes for biomolecules. Heterocycles such as pyrrole, imidazole and triazole are present in biological molecules such as Vitamine B12 and amino acids and could potentially target multiple biological processes. Considering this, we have explored the chemistry and biological properties of thiosemicarbazones series and their complexes bearing heterocycles such as pyrrole, imidazole, thiazole and triazole. We focus at the chemistry and cytotoxicity of those derivatives to find out the structure activity relationships, and particularly we analyzed those examples with the TSCN units in which the mechanism of action information has been profoundly studied and pathways determined, to promote future studies for heterocycle derivatives.

Efficient Emission in Halide Layered Double Perovskites: The Role of Sb3+ Substitution in Cs4Cd1–xMnxBi2Cl12 Phosphors

Layered halide perovskites and double perovskites optoelectronic properties have recently been the subject of intense research. Layered double perovskites represent the merging of both worlds, and as such, have the potential to further expand the already vast space of optoelectronic properties and applications of halide perovskites. Despite having more than 40 known members, to date, only the <111>-oriented layered double perovskites: Cs₄Cd₁–_xMn_x<b>Bi</b>₂Cl₁₂, have shown efficient photoluminescence (PL). In this work, we replaced Bi with Sb to further investigate the electronic structure and PL properties of these materials, resulting in two new families of layered inorganic perovskites alloys with full solubility. The first family, Cs₄Cd₁–_xMn<b>Sb</b>₂Cl₁₂, exhibits a PL emission at 605 nm ascribed to Mn²⁺ centers in octahedral coordination, and a maximum photoluminescence quantum yield PLQY of 28.5%. The second family of alloys, also with full solubility, Cs₄Cd_0.8Mn_0.2(Sb₁–_yBi_y)₂Cl₁₂, contains a fixed amount of Mn²⁺ and Cd²⁺ cations but different concentrations of the trivalent metals. This variability allows the tuning of the PL emission from 603 nm to 614 nm. We show that the decreased efficiency of the Cs₄Cd₁–_xMn_xSb₂Cl₁₂family compared to Cs₄Cd₁–_xMn_x<b>Bi</b>₂Cl₁₂, is mostly due to a decreased spin-orbit coupling in Sb and the subsequent increased electronic delocalization compared to the Bi alloys, reducing the energy transfer to Mn²⁺ centers. This work lays out a roadmap to understand and achieve high photoluminescence efficiencies in layered double perovskites.<p></p>