Functionalization of Biphenylcarbazole (CBP) with Siloxane-Hybrid Chains for Solvent-Free Liquid Materials

We report herein the synthesis of siloxane-functionalized CBP molecules (4,4′-bis(carbazole)-1,1′-biphenyl) for liquid optoelectronic applications. The room-temperature liquid state is obtained through a convenient functionalization of the molecules with heptamethyltrisiloxane chains via hydrosilylation of alkenyl spacers. The synthesis comprises screening of metal-catalyzed methodologies to introduce alkenyl linkers into carbazoles (Stille and Suzuki Miyaura cross-couplings), incorporate the alkenylcarbazoles to dihalobiphenyls (Ullmann coupling), and finally introduce the siloxane chains. The used conditions allowed the synthesis of the target compounds, despite the high reactivity of the alkenyl moieties bound to π-conjugated systems toward undesired side reactions such as polymerization, isomerization, and hydrogenation. The features of these solvent-free liquid CBP derivatives make them potentially interesting for fluidic optoelectronic applications.

A conversation on the quartic equation of the secular determinant of methylenecyclopropene

The Hückel method (HM) is based on quantum mechanics and it is used for calculating the energies of molecular orbitals of π electrons in conjugated systems. The HM involves the setting up of the secular determinant which is expanded to obtain a polynomial which is to be solved. In general, the polynomial is one which may be factorized. However, in May 2020, students brought to my attention that the secular determinant of methylenecyclopropene could not be factorized completely. As a result of this, we used a combination of online tools, technology and visualization to calculate the roots of the secular determinant. This write-up, in a playwriting format, describes the conversation between the facilitator and the students.

Functionalization of Biphenylcarbazole (CBP) with Siloxane-hybrid Chains for Solvent-Free Liquid Materials

We report herein the synthesis of siloxane-functionalized CBP molecules (4,4’-bis(carbazole)-1,1′-biphenyl) for liquid optoelectronic applications. The room-temperature liquid state is obtained through a convenient functionalization of the molecules with heptamethyltrisiloxane chains via hydrosilylation of alkenyl spacers. The synthesis comprises screening of metal-catalyzed methodologies to introduce alkenyl linkers into carbazoles (Stille and Suzuki Miyaura cross-couplings), incorporate the alkenylcarbazoles to dihalobiphenyls (Ullmann coupling), and finally introduce the siloxane chains. The used conditions allowed the synthesis of the target compounds, despite the high reactivity of the alkenyl moieties bound to π-conjugated systems toward undesired side reactions such as polymerization, isomerization, and hydrogenation. The features of these solvent-free liquid CBP derivatives make them potentially interesting for fluidic optoelectronic applications.

Photophysical Properties and Electronic Structure of Symmetrical Curcumin Analogues and Their BF2 Complexes, Including a Phenothiazine Substituted Derivative

Symmetrically substituted curcumin analogue compounds possess electron donor moieties at both ends of the conjugated systems; their difluoroboron complexes were synthesized, and their structures were fully characterized. A novel compound with enhanced photophysical properties bearing phenothiazine moieties is reported. The introduction of BF2 into the molecular structures resulted in bathochromic shifts both in the absorption and emission spectra, indicating that the π-conjugation was more extended than the one in the initial compounds. The solvatochromic effects were studied, which in case of the phenothiazinyl-curcumin BF2 complex was the most notable. Theoretical study of the investigated compounds was carried out using DFT and TD-DFT methods to evaluate the ground state geometries and vertical excitation energies.

A Brief Review on the High-Energy Electromagnetic Radiation-Shielding Materials Based on Polymer Nanocomposites

This paper revises the use of polymer nanocomposites to attenuate high-energy electromagnetic radiation (HE-EMR), such as gamma radiation. As known, high-energy radiation produces drastic damage not only in facilities or electronic devices but also to life and the environment. Among the different approaches to attenuate the HE-EMR, we consider the use of compounds with a high atomic number (Z), such as lead, but as known, lead is toxic. Therefore, different works have considered low-toxicity post-transitional metal-based compounds, such as bismuth. Additionally, nanosized particles have shown higher performance to attenuate HE-EMR than those that are micro-sized. On the other hand, materials with π-conjugated systems can also play a role in spreading the energy of electrons ejected as a consequence of the interaction of HE-EMR with matter, preventing the ionization and bond scission of polymers. The different effects produced by the interactions of the matter with HE-EMR are revised. The increase of the shielding properties of lightweight, flexible, and versatile materials such as polymer-based materials can be a contribution for developing technologies to obtain more efficient materials for preventing the damage produced for the HE-EMR in different industries where it is found.

Excited States Symmetry Breaking and In-Plane Polarization Cause Chiral Reversal in Diastereomers

In this work, we investigate the electronic transitions and chirality of three isomers of huge conjugated systems: asymmetric diastereomers (MMMM) and two symmetrical diastereomers (PMPM and PPMM). The physical mechanism of flipping has been studied theoretically. The new ribbon-shaped polycyclic aromatic hydrocarbons (PAHs) molecule is formed by connecting three graphene-like systems with large conjugated π orbitals. By calculating and analyzing electromagnetic interaction decomposition over distance, it can be found that the chirality reversal of different energies is caused by the symmetrical fracture of TMDM in the Z direction. The chirality reversal at the same energy is caused by the in-plane polarization of the TMDM along the Y direction.

Effects of Different Delocalized π-Conjugated Systems Towards the TiO2-Based Hybrid Photocatalysts

Modulating the structure of a photocatalyst at the molecular level can improve the photocatalytic efficiency and provides a guide for the synthesis of highly qualified photocatalysts. In this study, TiO2 was modified by various organic compounds to form different TiO2-based hybrid photocatalysts. 1,10-Phenanthroline (Phen) is an organic material with delocalized π-conjugated systems. It was used to modify TiO2 to form the hybrid photocatalyst Phen/TiO2. Furthermore, 1,10-phenanthrolin-5-amine (Phen-NH2) and 1,10-phenanthroline-5-nitro (Phen-NO2) were also used to modify TiO2 to form NH2-Phen/TiO2 and NO2-Phen/TiO2, respectively. The samples of TiO2, Phen/TiO2, NO2-Phen/TiO2, and NH2-Phen/TiO2 were carefully characterized, and their photocatalytic performance was compared. The results indicated that the photocatalytic efficiency followed the order of NH2-Phen/TiO2 > NO2-Phen/TiO2 > Phen/TiO2 > TiO2. It could be found that modifying TiO2 with different organic compounds containing delocalized π-conjugated systems could enhance the photocatalytic ability; furthermore, the level of this enhancement could be modulated by different delocalized π-conjugated systems.

Interaction of dirhenium(III) tryptophan complex compound with DNA and protein

We report about the interactions of dirhenium(III) compound cis-[Re2(Trp)2Cl4(CH3CN)2]Cl2 (I) with bovine serum protein (BSA) and guanine (G4) quadruplexes DNA by UV-Vis titration. Addition of I to BSA led to the interaction between these compounds with binding constant 5.6103 M–1 and hyperchromism (20.9%) of the main protein absorption band (280 nm). These results support our assumption about formation of the additional conjugated systems during the process of interaction with BSA. Stabilization of the quadruple bonded rhenium(III) complex compound was shown in the presence of BSA (the rate of destruction was reduced), that may be explained by interaction between amino acid residues of BSA and quadruple bond of dirhenium(III) complex compound. In addition, we have obtained data about strong hyperchromism (up to 100%) and significant shift of the maximum of absorption (blue shift) towards UV (2–9 nm) and visible (22 nm) regions in the spectra of mixtures G4s and I, that, in our opinion, correlated with a conformational change in DNA and with formation of additional conjugated systems around quadruple bond of I. In a whole, our work confirms the strong binding activity of a cluster dirhenium(III) compound towards G4 quadruplexes, that exceed the binding activity to proteins and witness to preferential interactions of I with G4 DNA in a living cell. These results may be used in DNA "silencing technology" and "antisense therapy".