TY - JOUR

T1 - Covalent Grafting of Eosin Y to the Giant Keplerate {Mo132} through an Organosilicon Linker in Homogeneous Regime

AU - Denikaev, Andrey

AU - Kim, Grigory

AU - Greshnyakov, Evgeny

AU - Moskalenko, Nikolai

AU - Grzhegorzhevskii, Kirill

N1 - The authors would like to acknowledge Alisa Shmidt for edits and feedback during the writing process and Yulia Gannochenko for graphical abstract’s design. The equipment of the Ural Center for Shared Use “Modern nanotechnology” Ural Federal University (Reg. no. 2968), which is supported by the Ministry of Science and Higher Education RF (project no. 075-15-2021-677), was used. Fluorescent, NMR, and CNH studies were carried out using the equipment of the Center for Joint Use “Spectroscopy and Analysis of Organic Compounds” at the Postovsky Institute of Organic Synthesis of the Russian Academy of Sciences (Ural Branch). This research was supported by the Russian Scientific Foundation, project no. 21-73-00311.

PY - 2023

Y1 - 2023

N2 - The template effect of giant polyoxometalates (POM) shows promising results towards the supramolecular design of hybrid materials suitable for photocatalytic reactions. Here, we demonstrate a novel synthetic approach for covalently grafting the xanthene dye eosin Y (EY) to the nanoscale Keplerate POM {Mo132} via an organosilicon linker (3-aminopropyltrimethoxysilane, APTMS) in a homogeneous regime. Using a phase transfer agent, tetrabutylammonium bromide, we solubilize the Keplerate POM modified with six {Si(CH2)3NH2} groups, {Mo132}@Si6, in a series of organic solvents—acetonitrile, acetone, tetrahydrofuran, and dichloromethane—to perform post-functionalization by using an NHS-ester of EY. Both IR and Raman spectroscopy affirm the preservation of the POM’s structure and showcase an amide bond formation between POM and EY in the obtained conjugate {Mo132}@Si6@EY@TBA. Grafting’s success is observed through significant downfield shifting of EY’s aromatic protons’ signals on the 1H NMR spectrum as compared to the spectra of EY and EY-NHS. The current synthetic approach enables us to exercise precise control of the stoichiometry in the POM-dye conjugates—1:1 for the POM-EY system—as confirmed by elemental analysis. Comprehensive photophysical analysis of {Mo132}@Si6@EY@TBA by means of UV-Vis and steady-state and time-resolved fluorescence measurements points to an existing strong interaction between molecular orbitals of EY and {Mo132}, leading to a photoinduced electron transfer, partial fluorescence quenching, and elongation of the excited state’s lifetime. These findings demonstrate that using APTMS as an organosilicon linker in tandem with the Keplerate POM as a nanoscale template can be readily applied as a routine synthetic procedure for grafting various organic dyes or other organic molecules bearing a carboxylic group in their structure to the giant POM surface in a variety of aprotic organic solvents.

AB - The template effect of giant polyoxometalates (POM) shows promising results towards the supramolecular design of hybrid materials suitable for photocatalytic reactions. Here, we demonstrate a novel synthetic approach for covalently grafting the xanthene dye eosin Y (EY) to the nanoscale Keplerate POM {Mo132} via an organosilicon linker (3-aminopropyltrimethoxysilane, APTMS) in a homogeneous regime. Using a phase transfer agent, tetrabutylammonium bromide, we solubilize the Keplerate POM modified with six {Si(CH2)3NH2} groups, {Mo132}@Si6, in a series of organic solvents—acetonitrile, acetone, tetrahydrofuran, and dichloromethane—to perform post-functionalization by using an NHS-ester of EY. Both IR and Raman spectroscopy affirm the preservation of the POM’s structure and showcase an amide bond formation between POM and EY in the obtained conjugate {Mo132}@Si6@EY@TBA. Grafting’s success is observed through significant downfield shifting of EY’s aromatic protons’ signals on the 1H NMR spectrum as compared to the spectra of EY and EY-NHS. The current synthetic approach enables us to exercise precise control of the stoichiometry in the POM-dye conjugates—1:1 for the POM-EY system—as confirmed by elemental analysis. Comprehensive photophysical analysis of {Mo132}@Si6@EY@TBA by means of UV-Vis and steady-state and time-resolved fluorescence measurements points to an existing strong interaction between molecular orbitals of EY and {Mo132}, leading to a photoinduced electron transfer, partial fluorescence quenching, and elongation of the excited state’s lifetime. These findings demonstrate that using APTMS as an organosilicon linker in tandem with the Keplerate POM as a nanoscale template can be readily applied as a routine synthetic procedure for grafting various organic dyes or other organic molecules bearing a carboxylic group in their structure to the giant POM surface in a variety of aprotic organic solvents.

UR - http://www.scopus.com/inward/record.url?partnerID=8YFLogxK&scp=85163749161

UR - https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=tsmetrics&SrcApp=tsm_test&DestApp=WOS_CPL&DestLinkType=FullRecord&KeyUT=001017286800001

U2 - 10.3390/inorganics11060239

DO - 10.3390/inorganics11060239

M3 - Article

VL - 11

JO - Inorganics

JF - Inorganics

SN - 2304-6740

IS - 6

M1 - 239

ER -