Organoboron Schiff bases as cell-staining fluorescent probes: Synthesis, Chemio-photophysical characterization, DFT, and X-ray structures: BOSCHIBAs, Low cytotoxicity, High photostability, Bioimaging

Tetra-coordinated organoboron complexes with triaminoguanidine-salicylidene based ligands: aggregation induced enhanced emission and mechanoresponsive features

Organoboron complexes have garnered significant attention due to their remarkable optical properties and diverse applications. However, synthesizing stable fused five-, six- and seven-membered organoboron complexes possess significant challenges. In this study, we successfully developed novel mono-nuclear (6-8 & 10) and di-nuclear (9) organoboron complexes supported by triaminoguanidine-salicylidene based C3-symmetric Schiff base ligands via one-step condensation reaction with excess phenylboronic acid. Single-crystal X-ray diffraction analysis revealed that in the mononuclear complexes (6-8 & 10), boron atoms adopt tetrahedral geometry with fused five-membered N-B-N and six-membered O-B-N chelate ring whereas in the dinuclear complex (9), two boron atoms exist in distinct coordination environment, forming four fused boron-incorporated rings, including six-membered N-B-N, six-membered O-B-N, seven-membered N-B-O and five-membered N-B-N chelate rings. Our findings provide a unique family of mononuclear organoboron complexes and dinuclear organoboron complex with ESIPT unit. Aggregation induced enhanced emission features of the compounds were established in THF-water mixture and supported by DLS and SEM analyses. Interestingly, compound 6, 9 and 10 shows interesting mechanoresponsive features upon grinding.

Multicomponent synthesis of chromophores – The one-pot approach to functional π-systems

Multicomponent reactions, conducted in a domino, sequential or consecutive fashion, have not only considerably enhanced synthetic efficiency as one-pot methodology, but they have also become an enabling tool for interdisciplinary research. The highly diversity-oriented nature of the synthetic concept allows accessing huge structural and functional space. Already some decades ago this has been recognized for life sciences, in particular, lead finding and exploration in pharma and agricultural chemistry. The quest for novel functional materials has also opened the field for diversity-oriented syntheses of functional π-systems, i.e. dyes for photonic and electronic applications based on their electronic properties. This review summarizes recent developments in MCR syntheses of functional chromophores highlighting syntheses following either the framework forming scaffold approach by establishing connectivity between chromophores or the chromogenic chromophore approach by de novo formation of chromophore of interest. Both approaches warrant rapid access to molecular functional π-systems, i.e. chromophores, fluorophores, and electrophores for various applications.

Boron Schiff bases derived from α-amino acids as nucleoli/cytoplasm cell-staining fluorescent probes in vitro

The size, shape, and number of nucleoli in a cell's nucleus might help to distinguish a malignant from a benign tumor. Cellular biology and histopathology often require better visualization to understand nucleoli-related processes, thus organelle-specific fluorescent markers are needed. Here, we report the design, synthesis, and fully chemo-photophysical characterization of fluorescent boron Schiff bases (BOSCHIBAs), derived from α-amino acids (i.e., phenylalanine, tyrosine and tryptophan), with nucleoli- and cytoplasm-specific staining in cells. It is the first time that Boron Schiff bases derived from α-amino acids act as notorious dual (nucleoli and cytoplasm) cell-staining fluorescent probes. The boron derivatives not only showed good photostability and acceptable quantum yields (∼5%) in solution, but also exhibited low cytotoxicity (>90% cell viability at 0.1 and 1 μg mL^-1), which make them good candidates to be used in medical diagnosis.