Synthesis, photophysical, electrochemical, and non-linear optical properties of triaryl pyrazole based B-N coordinated boron compounds

We report here a set of triaryl pyrazole based B-N coordinated boron compounds ( 11 - 17 ) synthesized by electrophilic aromatic borylation strategy. All the pyrazole boron compounds were thoroughly characterized using multinuclear NMR spectroscopy, LCMS, and single crystal X-ray diffraction analysis (for 12 - 17 ). The photoluminescence measurements of 11 - 17 revealed that the emission peak maxima were tuned based on the substitution on Nphenyl. The photophysical and electrochemical properties were further supported by theoretical calculations. Z-scan based investigations at 515 nm pump wavelength showed that B-N coordination led to enhancement of nonlinear absorption (two-photon absorption (TPA)) in these compounds if an electron deficient moiety is attached. It has also been observed that an appropriate choice of moiety allows to optimally maneuver the molecular polarizability of the π-system and consequently, assists in controlling the third-order nonlinear optical response.

Highly Fluorescent Dianionic Polymethines with a 1,3,2-Dioxaborine Core

The difluoroboron β-diketonate ring is ever more used for creating bright polymethine-type fluorophores for the visible and NIR range. Here, we report the synthesis and spectral properties of a series of dianionic cyanine dyes of the rare A¹-π-A-π-A¹ type, with the central dioxaborine ring (A) embedded into the polymethine chain and various electron-acceptor terminal groups A¹. Depending on the nature of the end group, the maxima of their intensive (with molar extinctions up to 380 000 M^-1 cm^-1) and narrow long-wavelength absorption band lie in the range of 530-770 nm. Their absorption and fluorescence bands are nearly mirror-like and characterized by weak solvatochromism; the marked hypsochromic shifts are observed only when going from polar aprotic solvents to methanol. The designed dianionic dyes have fluorescence quantum yields up to 92 % in the visible range, and even for the NIR dyes, the values of 18-37 % are observed in DMF.

Synthesis of π-extended B ← N coordinated phenanthroimidazole dimers and their linear and nonlinear optical properties

B ← N coordinated phenanthroimidazole dimers exhibit excellent fluorescence quantum yields in solution and conjugation length dependant two-photon-absorption properties.

BF2 complexes of 1,3-diketones on the surface of phosphorus dendrimers: synthesis and study of the photoluminescence properties

Difluoroboron complexes of monomeric and dimeric diketones and of generations 0–4 of phosphorus dendrimers ended by diketone ligands are synthesized and characterized. Their photoluminescence properties are measured. All compounds exhibit an intense absorption band in the near UV region. Both model dimers and dendrimers show a marked hypsochromic shift of this absorption band compared with the monomeric difluoroboron complex. The fluorescence of the dioxaborine complex subunit in the multichromophoric dendritic architectures is quenched compared with the emission of the isolated monomeric fluorophore, presumably due to interactions between the terminal groups of dendrimers.

A curcumin-based TPA four-branched copper(II) complex probe for in vivo early tumor detection

A multibranched Cu(II) complex CuL2 curcumin-based was synthesized and characterized by single-crystal X-ray diffraction analysis. The photophysical properties of the complex have been investigated both experimentally and theoretically. The results show that the target complex exhibits higher quantum yield and larger two-photon absorption (TPA) cross-section in the near infrared (NIR) region compared with its free ligand. The cell imaging studies in vitro and in vivo reveal that the complex shows good photostability and excellent tumor targeting capability to tested cancerous cells, which can be potentially used for early tumor detection.

25th anniversary article: Design of polymethine dyes for all-optical switching applications: guidance from theoretical and computational studies

All-optical switching--controlling light with light--has the potential to meet the ever-increasing demand for data transmission bandwidth. The development of organic π-conjugated molecular materials with the requisite properties for all-optical switching applications has long proven to be a significant challenge. However, recent advances demonstrate that polymethine dyes have the potential to meet the necessary requirements. In this review, we explore the theoretical underpinnings that guide the design of π-conjugated materials for all-optical switching applications. We underline, from a computational chemistry standpoint, the relationships among chemical structure, electronic structure, and optical properties that make polymethines such promising materials.