Contrasting ground- and excited-state intramolecular aggregation in choline chloride-based deep eutectic solvents versus a liquid polymer

Abstract

The pyrenyl (Py) groups in several dipyrenyl (or bispyrenyl) compounds, while do not dimerize in the ground-state, are known to intramolecularly aggregate exclusively in the excited-state to form excimers in...

Intramolecular dimer formation reveals anomalous solvation within fluorous solvent perfluorodecalin

“…Earlier, ground-state dimerization was also reported by our group in highly viscous polar choline chloride-based deep eutectic solvents (DESs) and glycerol (Z = 1412.0 mPa s; at 293.15 K), but dimerization was observed neither in comparatively less viscous PDMS2000 (Z = 21.4 mPa s; at 293.15 K) solutions nor in ionic liquids. 27,28 Since PFD is highly non-polar and has considerably less dynamic viscosity in comparison to DESs and glycerol as well as PDMS2000, the unusual outcome of groundstate dimerization cannot be generalized to viscosity dependence or solubility dependence but is specific to the fluorous solvent PFD. The unfavourable solvation of BPP within PFD is tentatively attributed to be the cause of this -in n-hexaneadded PFD, the probe BPP may be preferentially solubilized by the n-hexane (vide infra).…”

“…The fact that the two scans do not overlap indicates the presence of intramolecular dimers of BPP in the ground state. 28,33,35 In the fluorous solvent PFD, the propane chain folds such that the two termini Py aggregate in the ground state. Importantly, a new bathochromic band also appears in the excitation scan acquired with λ em = 480 nm characterizing the ground-state intramolecular aggregates.…”

“…[21][22][23][24] The efficiency and dynamics of intramolecular dimerization is found to be highly sensitive toward the solubilizing media and temperature, based on published reports in certain liquid polymers, ionic liquids (ILs), and deep eutectic solvents (DESs) along with organic solvents. 21,[25][26][27][28] As the solubilizing milieu and temperature critically control the intramolecular dimerization in BPP, we investigated the dimerization efficiency and dynamics as a function of temperature (293.15-333.15 K) in neat PFD. To the best of our knowledge, this is the first report on the investigation of Py-Py intramolecular dimerization in fluorous media.…”

“…21–24 The efficiency and dynamics of intramolecular dimerization is found to be highly sensitive toward the solubilizing media and temperature, based on published reports in certain liquid polymers, ionic liquids (ILs), and deep eutectic solvents (DESs) along with organic solvents. 21,25–28…”

Highly Efficient Intramolecular Excimer Formation in a Disulfide-Linked Dipyrenyl Compound: Proton Recognition and Fluidity Assessment

“…The rate constant for monomer deactivation ( k M ) was obtained from the excited-state emission intensity decay of 1-methylpyrene (1-MePy) under identical conditions. ,,, Based on previous reports, the fluorescence lifetime (τ 1‑MePy ) of 1-MePy is approximated as the monomer decay time of DTP as it does not undergo intramolecular excimer formation (excited-state intensity decay of 1-MePy fits best to the single-exponential decay function; k M = 1/τ 1‑MePy ). From I M ( t ) and I E ( t ) of DTP and I ( t ) of 1-MePy acquired within aforementioned solvents under ambient conditions, the rate constants k a , k d , k E , and k M are estimated and are presented in Table .…”