TY - JOUR

T1 - N,O-boron spirocyclic complexes: How electronic and spatial factors modulate photophysical and physicochemical properties

AU - Motverov, Maxim V.

AU - Lugovik, Kseniya I.

AU - Vataru, Galina V.

AU - Minin, Artem S.

AU - Benassi, Enrico

AU - Belskaya, Nataliya P.

N1 - This work was carried out using the equipment of the Shared Research Centre of Scientific Equipment SRC IIP UrB RAS. Computational resources were kindly provided by the HPCC of Nazarbayev University, Astana, Kazkhstan.

PY - 2025/4

Y1 - 2025/4

N2 - This study presents the synthesis of new spirocyclic boron-coordinated (SBCs) fluorophores based on a simple and facile procedure and their optical properties. The structure of the complexes was confirmed by 1H, 13C, 11B NMR spectra, high resolution mass spectra and single crystal X-ray diffraction data. The effect of the substituents in the terminal aromatic cycles and the spirocycle size on the photophysical properties was investigated by a combined experimental and computational approach. The absorption and fluorescence emission properties of the SBCs were investigated and the results obtained revealed evident relationships between the electronic nature of the substituents and their photophysical properties. These differences clearly divide the spirocomplexes into two groups with significant differences in absorption and emission properties. SBCs with an electron acceptor substituent in cycle A and an electron donor substituent in cycle B have an emission maximum in the shorter wavelength region (416–451 nm) and a quantum yield of 2.3–12.5 %. In another group of compounds with the opposite set of substituents in cycles A and B, the emission maximum is located at 469–560 nm, the quantum yield is much lower (0.1–0.4 %), but the Stokes shift (8114-8160 cm−1) increases significantly. These differences were explained using state-of-the-art quantum chemical calculations, which show that SBCs differ in the values of the electronic charges transferred in ESs (S1v and S1r) and their localisation, and have different conjugated systems. SBCs exhibited increased quantum yield with increasing medium viscosity, under mycelial formation conditions, and significant aggregation-enhanced emission behaviour in THF-H2O and DMSO-H2O mixtures, along with excellent solid-state photophysical properties. Cellular uptake and cytotoxicity studies using Vero cells showed that SBCs are biocompatible and selectively accumulate in cell lipid droplets, endoplasmic reticulum, Golgi apparatus and mitochondria.

AB - This study presents the synthesis of new spirocyclic boron-coordinated (SBCs) fluorophores based on a simple and facile procedure and their optical properties. The structure of the complexes was confirmed by 1H, 13C, 11B NMR spectra, high resolution mass spectra and single crystal X-ray diffraction data. The effect of the substituents in the terminal aromatic cycles and the spirocycle size on the photophysical properties was investigated by a combined experimental and computational approach. The absorption and fluorescence emission properties of the SBCs were investigated and the results obtained revealed evident relationships between the electronic nature of the substituents and their photophysical properties. These differences clearly divide the spirocomplexes into two groups with significant differences in absorption and emission properties. SBCs with an electron acceptor substituent in cycle A and an electron donor substituent in cycle B have an emission maximum in the shorter wavelength region (416–451 nm) and a quantum yield of 2.3–12.5 %. In another group of compounds with the opposite set of substituents in cycles A and B, the emission maximum is located at 469–560 nm, the quantum yield is much lower (0.1–0.4 %), but the Stokes shift (8114-8160 cm−1) increases significantly. These differences were explained using state-of-the-art quantum chemical calculations, which show that SBCs differ in the values of the electronic charges transferred in ESs (S1v and S1r) and their localisation, and have different conjugated systems. SBCs exhibited increased quantum yield with increasing medium viscosity, under mycelial formation conditions, and significant aggregation-enhanced emission behaviour in THF-H2O and DMSO-H2O mixtures, along with excellent solid-state photophysical properties. Cellular uptake and cytotoxicity studies using Vero cells showed that SBCs are biocompatible and selectively accumulate in cell lipid droplets, endoplasmic reticulum, Golgi apparatus and mitochondria.

KW - AIEE

KW - Bioimaging

KW - N,O-boron complexes

KW - SSEE

KW - Spirocycles

KW - Viscosity sensor

UR - https://www.mendeley.com/catalogue/7a617dfd-456a-3b8d-b2f6-3cf9d876bfc9/

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85214301992&origin=inward&txGid=30661e65b217e1a23ac33bb9d43cdca5

U2 - 10.1016/j.dyepig.2024.112622

DO - 10.1016/j.dyepig.2024.112622

M3 - Article

VL - 235

JO - Dyes and Pigments

JF - Dyes and Pigments

SN - 0143-7208

M1 - 112622

ER -