Molecular rotors of naphthalimide and benzodithiophene as effective solvent polarity probes, temperature sensors, and for g‐C3N4 sensitization

• Published in: Photochemistry and photobiology Vol. 100; no. 4; pp. 1055 - 1067
• Main Authors: Kumari, Anita, Sharma, Sushil, Sengupta, Sanchita
• Format: Journal Article
• Language: English
• Published: Lawrence Blackwell Publishing Ltd 01-07-2024
• Subjects: 1,8‐naphthalimide; benzodithiophene; Biomimetics; Carbon nitride; Charge transfer; Chemical reactions; Chemical synthesis; Chloroform; composite; Coupling (molecular); Emission spectra; Medical imaging; Microenvironments; molecular rotor; Photocatalysis; Rotors; Solvents; Spectral sensitivity; Temperature; Temperature sensors
• ISSN: 0031-8655; 1751-1097; 1751-1097
• DOI: 10.1111/php.13931

Acceptor–donor–acceptor (A–D–A) molecular rotors have drawn substantial attention for their applications in monitoring temperature variations within cellular microenvironments, biomimetic photocatalysis, and bioimaging. In this study, we have synthesized two novel rotor molecules, NBN1 and NBN2, by incorporating benzodithiophene (BDT) as the donor core and naphthalic anhydride/naphthalimide (NA/NI) moieties as acceptors using Pd‐catalyzed Stille coupling reactions. These molecules exhibited distinct charge transfer (CT) behavior in both their absorption and emission spectra and displayed prominent emission solvatochromism. Notably, NBN1 exhibited better CT properties among the two molecules. Moreover, these A–D–A molecular rotors demonstrated remarkable sensitivities of their emission spectra toward solvent polarities and temperatures. Rotors NBN1 and NBN2 showed positive temperature coefficients with internal temperature sensitivities of 0.34% °C−1 and 0.13% °C−1 in chloroform, respectively, and thus hold significant promise for detecting temperature variations in cellular microenvironment. Furthermore, we have modeled these molecules with graphitic carbon nitride (g‐C3N4) to form composite systems and performed theoretical calculations to obtain valuable insights into their charge transfer behavior. Theoretical results suggested that these molecules have the potential to efficiently sensitize and modulate the band gap of g‐C3N4 and show potential for diverse photocatalytic applications.
Acceptor–donor–acceptor molecular rotors based on benzothiophene (BDT) as donors and Napthalimides as acceptors were synthesized that exhibit efficient charge transfer properties. These rotors are potential solvent polarity probes and temperature sensors. Theoretical calculations revealed these can sensitize g‐C3N4 to boost the latter's optoelectronic properties and facilitate photocatalytic hydrogen production.