Synthesis, Structure, and Optical Properties of 1,4-Dithiafulvene-Based Nonlinear Optic-phores

Molecularly Engineered Multifunctional Bridging Layer Derived from Dithiafulavene Capped Spiroxanthene for Stable and Efficient Perovskite Solar Cells

This study introduces a novel approach centered around the design and synthesis of an interfacial passivating layer in perovskite solar cells (PSCs). This architectural innovation is realized through the development of a specialized material, termed dithiafulvene end-capped Spiro[fluorene-9,9'-xanthene], denoted by the acronym AF32. In this design architecture, dithiafulvene is thoughtfully attached to the spiroxanthene fluorene core with phenothiazine as the spacer unit, possessing multiple alkyl chains. AF32 passivates interfacial defects by coordinating the sulfur constituents of the phenothiazine and dithiafulvene frameworks to the uncoordinated Pb2+ cations on the surface of the perovskite film, and the alkyl chains construct a hydrophobic environment, preventing moisture from entering the hydrophilic perovskite layer and improving the long-term stability of PSCs. Furthermore, this conductive interlayer facilitates hole transport in PSCs due to its well-aligned molecular orbital levels. Such improvements translated into an enhanced power conversion efficiency (PCE) of 22.6% for the device employing 1.5 mg/mL AF32, and it maintained 85% of its initial PCE after more than 1800 h under ambient conditions [illumination and 45 ± 5% relative humidity (RH)]. This study not only marks progress in photovoltaic technology but also expands our understanding of manipulating interfacial properties for optimized device performance and stability.

Studies of a bola-type bis(dithiafulvene) molecular system: synthesis, crystal structure, and electrochemical properties

A bis(dithiafulvene) compound that contains a 1,3-diphenoxypropane central unit was designed and investigated in this work.

Selective functionalization of the 1H-imidazo[1,2-b]pyrazole scaffold. A new potential non-classical isostere of indole and a precursor of push-pull dyes

We report the selective functionalization of the 1H-imidazo[1,2-b]pyrazole scaffold using a Br/Mg-exchange, as well as regioselective magnesiations and zincations with TMP-bases (TMP = 2,2,6,6-tetramethylpiperidyl), followed by trapping reactions with various electrophiles. In addition, we report a fragmentation of the pyrazole ring, giving access to push-pull dyes with a proaromatic (1,3-dihydro-2H-imidazol-2-ylidene)malononitrile core. These functionalization methods were used in the synthesis of an isostere of the indolyl drug pruvanserin. Comparative assays between the original drug and the isostere showed that a substitution of the indole ring with a 1H-imidazo[1,2-b]pyrazole results in a significantly improved solubility in aqueous media.

Recent advances in dithiafulvenyl-functionalized organic conjugated materials

This review highlights the recent studies of advanced organic π-conjugated materials that contain 1,4-dithiafulvene (DTF) as a redox-active component.

Achieving the highest efficiency using a BODIPY core decorated with dithiafulvalene wings for small molecule based solution-processed organic solar cells

A novel boron dipyrromethene based dye, coded as BODIPY-DTF, decorated with dithiafulvalene wings has been developed for solar cell application.

Intramolecular alkyne–dithiolium cycloaddition: a joint experimental and DFT mechanistic study

The intramolecular alkyne–dithiolium cycloaddition reactions were found to occur through either a concerted or stepwise pathway, depending on the conjugation degree of the alkynyl unit.

Synthesis of dithiafulvene-quinone donor-acceptor systems: isolation of a Michael adduct

π-Conjugated donor-acceptor systems based on dithiafulvene (DTF) donor units and various acceptor units have attracted attention for their linear and nonlinear optical properties. The reaction between p-benzoquinone and a 1,3-dithiole phosphonium salt, deprotonated by lithium hexamethyldisilazide (LiHMDS), gave a product mixture from which the Michael adduct [systematic name: dimethyl 2-(3-hydroxy-6-oxocyclohexa-2,4-dien-1-ylidene)-2H-1,3-dithiole-4,5-dicarboxylate], C13H10O6S2, was isolated. It is likely that one of the unidentified products obtained previously by others from related reactions could be a similar Michael adduct.

Aromatic/proaromatic donors in 2-dicyanomethylenethiazole merocyanines: from neutral to strongly zwitterionic nonlinear optical chromophores

Push-pull compounds, in which a proaromatic electron donor is conjugated to a 2-dicyanomethylenethiazole acceptor, have been prepared, and their properties compared to those of model compounds featuring an aromatic donor. A combined experimental (X-ray diffraction, (1) H NMR, IR, Raman, UV/Vis, nonlinear optical (NLO) measurements) and theoretical study reveals that structural and solvent effects determine the ground-state polarisation of these merocyanines: whereas 4H-pyran-4-ylidene- and 4-pyridylidene-containing compounds are zwitterionic and 1,3-dithiol-2-ylidene derivatives are close to the cyanine limit, anilino-derived merocyanines are essentially neutral. This very large range of intramolecular charge transfer (ICT) gives rise to efficient second-order NLO chromophores with μβ values ranging from strongly negative to strongly positive. In particular, pyranylidene derivatives are unusual in that they show an increase in the degree of ICT on lengthening the π-spacer, a feature that lies behind the very large negative μβ values they display. The linking of the formally quinoidal 2-dicyanomethylenethiazole moiety to proaromatic donors seems a promising approach towards the optimisation of zwitterionic NLO chromophores.

Linear and V-shaped nonlinear optical chromophores with multiple 4H-pyran-4-ylidene moieties

A simple synthesis of dipolar one- and two-dimensional chromophores bearing two or three 4H-pyran-4-ylidene moieties is reported. Whereas the pyranylidene fragments acting as donors are proaromatic, the spacer one is not. In the linear derivatives, chain elongation gives rise to a sharp increase in the second order nonlinear optical responses, but some V-shaped derivatives display first hyperpolarizabilities (beta) lower than those of their linear analogues. This uncommon feature lends experimental support to previous theoretical studies on the relative contribution and sign of the beta-tensor components.

4H-Pyran-4-ylidenes: strong proaromatic donors for organic nonlinear optical chromophores

Merocyanines where a polyenic spacer separates a 4H-pyran-4-ylidene moiety and different strong organic acceptors have been synthesized. According to NMR studies and X-ray diffraction data, these compounds have weakly alternated structures and remarkably zwitterionic ground states, with a partial aromatic character that is compared to those of other pyran derivatives. The proaromaticity of the 4H-pyran-4-ylidene donor lies behind the cyanine-like behavior and low (positive or negative) second-order optical nonlinearities of the shorter derivatives. On the other hand, lengthening the pi-spacer gives rise to rapidly increasing mubeta(1907) values up to 17,400 x 10(-48) esu.