Second harmonic generation from tetraphenylethylene functionalized graphdiyne

The nonlinear optical properties of two-dimensional (2D) layered materials have received extensive attention for their promising application prospects in the field of optoelectronics. Among these materials, 2D carbon materials have been pushed to the research hotspot thanks to their unique chemical and electronic structures. However, the exploration of second harmonic generation (SHG) is currently limited to sp2 hybridized 2D carbon materials, while the research on multi-hybridized carbon atomic materials is relatively rare. Here, we report the observation of optical second harmonic from tetraphenylethylene-graphdiyne (TPE-GDY), a fully conjugated fluorescent 2D material composed of sp and sp2 hybridized carbon atoms based on the tetraphenylethylene (TPE) unit. TPE-GDY is mixed with polyvinylpyrrolidone (PVP) to prepare TPE-GDY/PVP nanocomposite films, which further improves the stability of TPE-GDY. Cotton effect and favorable SHG response have been observed from these composite films. Our research enriches the material system in the field of nonlinear optical effects and opens up broad prospects for functional and potential applications of 2D graphdiyne materials.

Photoresponsive chiral vesicles as a light harvesting matrix with tunable chiroptical properties

Self-assembled vesicles show photoresponsive Cotton effect and CPL activities, which also perform as a matrix for energy transfer-based CPL material.

Correlations between ECD spectra and absolute configuration of bridged-ring lactones: Revisiting Beecham’s rule

Bridged lactones frequently appear as structural fragments in natural products. To elucidate their stereochemistry using electronic circular dichroism (ECD) spectra, Beecham correlated the sign of the Cotton effect (CE) from...

Chiral approach to investigate mechanism of highly efficient thermally activated delayed fluorescence

Cancellation of the Cotton effect depending on vibrations of a chiral orthogonal donor–acceptor structure identifies a mechanism of highly efficient delayed fluorescence.

Kinetic Investigation on Tetrakis(4-Sulfonatophenyl)Porphyrin J-Aggregates Formation Catalyzed by Cationic Metallo-Porphyrins

Under mild acidic conditions, various metal derivatives of tetrakis(4-N-methylpyridinium)porphyrin (gold(III), AuT4; cobalt(III), CoT4; manganese(III), MnT4 and zinc(II), ZnT4) catalytically promote the supramolecular assembling process of the diacid 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H2TPPS4) into J-aggregates. The aggregation kinetics have been treated according to a well-established model that involves the initial formation of a critical nucleus containing m porphyrin units, followed by autocatalytic growth, in which the rate evolves as a power of time. An analysis of the extinction time traces allows to obtain the rate constants for the auto-catalyzed pathway, kc, and the number of porphyrins involved in the initial seeding. The aggregation kinetics have been investigated at fixed H2TPPS4 concentration as a function of the added metal derivatives MT4. The derived rate constants, kc, obey a rate law that is first order in [MT4] and depend on the specific nature of the catalyst in the order AuT4 > CoT4 > MnT4 > ZnT4. Both resonance light scattering (RLS) intensity and extinction in the aggregated samples increase on increasing [MT4]. With the exception of AuT4, the final aggregated samples obtained at the highest catalyst concentration exhibit a negative Cotton effect in the J-band region, evidencing the occurrence of spontaneous symmetry breaking. The role of the nature of the metal derivative in terms of overall charge and presence of axial groups will be discussed.

The Chiral 1:2 Adduct (S)S(S)C(−)589-Ethyl 2-Phenylbutyl Sulphide-Mercury (II) Chloride:(−)589[(S)S(S)C-Et(2-PhBu)S.(HgCl2)2]. Stereoselective Synthesis, Asymmetric Oxidation, Crystal and Molecular Structure and Circular Dichroism Spectra

Optically active (−)589ethyl (S)-2-phenylbutyl thioether, (−)(S)C-Et(PhBu)S (I), and its new diastereoisomeric mercury (II) chloride adduct, 1:2, (−)[(S)S(S)C-Et(PhBu)S.(HgCl2)2]2, (II) were stereoselectively synthesized; the absorbance (UV) and circular dichroism (CD) spectra were measured and the crystal and molecular structure of complex (II) was determined by single-crystal X-ray diffraction. Two different Hg centres are present whose coordination environments are built by two short bonds to chloride ligands in one case, and to one chloride and one sulphur in the other one. These originate digonal units. Electroneutrality is achieved by a further chlorine, which can be considered prevalently ionic and bonded to the two Hg centres, forming square bridging systems nearly perpendicular to the digonal molecules. The coordination polyhedra can be interpreted as 2 + 4 tetragonally-compressed octahedra with the four longer contacts lying in the equatorial plane. IR spectroscopic data are consistent with the presence of one bent and one linear Cl–Hg–Cl moiety. The absolute configurations at both stereogenic centres of the formed diastereoisomeric complex (II) are (S). The (S)S absolute configuration at the stereogenic sulphur atom bonded to the mercury(II) atom in complex (II) has been related with the negative Cotton effect assigned in its circular dichroism (CD) spectrum to a charge-transfer transition at ca. 230 nm. The stereoselective oxidation of (I) and (II) with hydrogen peroxide, induced by the stereogenic carbon atom (S)C of the enantiopure sulphide, gave (−)598ethyl (S)C-2-phenylbutyl(S)S-sulphoxide, (−)598[(S)S(S)C-Et(PhBu)SO], (III), having 18.1% de. Oxidations carried out in the presence of a 200 molar excess of mercury(II) chloride gave (−)598ethyl (S)C-2-phenylbutyl(R)S-sulphoxide, (−) 598[(R)S(S)C-Et(PhBu)SO], (IV) with 31% de, showing the cooperative influence of mercury(II) chloride on the selectivity of the oxidation reaction.