title: Supramolecular interaction of coumarin 1 dye with cucurbit[7]uril as host: combined experimental and theoretical study.
abstract: Molecules of the coumarin family have fluorescence characteristics that are highly sensitive to their environment, and thus, they have been used as fluorescent sensors in chemical and biological systems. However, the very poor fluorescence yield of most coumarin dyes in aqueous media limits their applications. We have adopted a supramolecular strategy to improve the fluorescence intensity of coumarin dye through its interaction with the relatively new host cucurbit[7]uril (CB[7]). The virtually nonfluorescent coumarin 1 (Φ(f) = 0.04) was converted into a highly fluorescent (Φ(f) = 0.52) entity in water upon addition of the nonfluorescent host CB[7]. Various spectroscopy techniques, namely, UV-vis absorption and steady-state and time-resolved fluorescence spectroscopies, established the formation of a strong 1:1 dye-CB[7] inclusion complex with a high binding constant of (1.2 ± 0.1) × 10(5) M(-1) for the dye. The stable inclusion complex of the neutral molecule was supported by density-functional-theory- (DFT-) based quantum chemical calculations. Energy decomposition analysis of various interaction factors in the host-guest complex revealed that key components providing stability to the complex were electrostatic, polarization, and charge-transfer energies. These new results on the formation of a strong inclusion complex of the versatile fluorophore coumarin 1 with the nontoxic host CB[7] could lead to the design of efficient molecular-scale biological probes, sensors, and photostable aqueous UV dye lasers.
authors.affiliation: Laser & Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai-400 085, India.
authors.forename: Monika
authors.initials: M
authors.lastname: Gupta
authors.forename: Dilip K
authors.initials: DK
authors.lastname: Maity
authors.forename: Manoj K
authors.initials: MK
authors.lastname: Singh
authors.forename: Sandip K
authors.initials: SK
authors.lastname: Nayak
authors.forename: Alok K
authors.initials: AK
authors.lastname: Ray
mesh_terms: D001952:Bridged-Ring Compounds / Q000737:chemistry*; D003374:Coumarins / Q000737:chemistry*; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D012399:Rotation; D013816:Thermodynamics; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils
chemical_list: D001952:Bridged-Ring Compounds; D003374:Coumarins; D005456:Fluorescent Dyes; D007093:Imidazoles; C456276:cucurbit(7)uril; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils