Room Temperature Phosphorescence in Solution from Thiophene-Bridged Triply Donor-Substituted Tristriazolotriazines

Most organic room-temperature phosphorescence (RTP) emitters do not show their RTP in solution. Here, we incorporated sulfur-containing thiophene bridges between the donor and acceptor moieties in D₃ A-type tristriazolotriazines (TTTs). The thiophene inclusion increased the spin-orbit coupling associated with the radiative T₁ →S₀ pathway, allowing RTP to be observed in solution for all compounds, likely assisted by protection of the emissive TTT-thiophene core from the environment by the bulky peripheral donors.

Impact of Substitution Pattern and Chain Length on the Thermotropic Properties of Alkoxy-Substituted Triphenyl-Tristriazolotriazines

Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropic properties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching in the chain and swallow-tails, are compared. Generally, these disks display broad and stable thermotropic mesophases, with the tangential TTT being superior to the radial isomer. The structure-property relationships of the number of alkyl chains, their position, length and structure were studied.

Synthesis, Thermal, and Optical Properties of Tris(5-aryl-1,3,4-oxadiazol-2-yl)-1,3,5-triazines, New Star-Shaped Fluorescent Discotic Liquid Crystals

The synthesis of tris(aryloxadiazolyl)triazines (TOTs), C₃‐symmetrical star‐shaped mesogenes with a 1,3,5‐triazine center, 5‐phenyl‐1,3,4‐oxadiazole arms, and various peripheral alkoxy side chains is reported. Threefold Huisgen reaction on a central triazine tricarboxylic acid and suitable aryltetrazoles yields the title compounds. Selected analogues with a benzene center are included in this study and allow for an evaluation of the impact of the central unit on the physical properties. Thermal (differential scanning calorimetry, DSC; polarization optical microscopy, POM), optical (UV/Vis, fluorescence), electric (time of flight, TOF), and structural (single crystal; wide‐angle X‐ray scattering, WAXS) properties of these compounds were investigated. The modification of alkoxy chain length and substitution pattern allows for a tuning of the physical properties. TOTs emit blue to yellow light, depending on conjugation length, donor–acceptor substitution, and solvent polarity, whereas concentration quenches and aggregation enhances the emission. The width of the mesophases is typically around ΔT=100–150 K but can even exceed 220 K. Polarization optical microscopy and X‐ray diffraction on oriented filaments reveal that TOTs are highly ordered liquid crystals (LCs) with long‐range hexagonal columnar structure.

Columnar self-assembly of N,N′,N′′-trihexylbenzene-1,3,5-tricarboxamides investigated by means of NMR spectroscopy and computational methods in solution and the solid state

The columnar self-assembly resulting from units of N,N′,N′′-trihexylbenzene-1,3,5-tricarboxamide is investigated in solution and the solid state by means of NMR spectroscopy and DFT methods.

Using Density Functional Theory To Study Neutral and Ionized Stacked Thymine Dimers

Stacking interactions in thymine dimers are studied with density functional theory. According to our calculations, six dimers of comparable stability can be prepared at low temperature, but dimerization is impossible at room temperature due to the large entropy contribution that accompanies it. Analysis of vibrational anharmonic coupling terms shows that each of the dimers exhibits distinct vibrational dynamics. Properties of electron density in the intermolecular region are used to analyze neutral stacked species and their ionized forms. Bond paths and critical points in the intermolecular region are identified, but a simple relationship between binding energy and total electron density in the intermolecular critical points could not be found due to an uneven electron distribution in the binding region. The reduced density gradient was confirmed to be a useful tool for analysis of weak stacking interactions. Those interactions also affect vertical and adiabatic ionization energies, which are computed to be slightly lower for the dimers compared to the monomer.

Tuning the photophysical properties of 4′-substituted terpyridines – an experimental and theoretical study

Several 2,2′:6′,2′′-terpyridine derivatives were synthesized and their photophysical properties were investigated by absorption and photoluminescence spectroscopy.

Structure and optoelectronic properties of helical pyridine–furan, pyridine–pyrrole and pyridine–thiophene oligomers

The optoelectronic properties of helical structures pyridine–furan, pyridine–pyrrole and pyridine–thiophene oligomers are explored using density functional theory methods.