Solvatochromism of a Novel Betaine Dye Derived from Purine

Abstract

A novel solvatochromic betaine dye has been synthesized from xanthosine and characterized spectroscopically by UV-vis in a broad range of solvents. The dye 9-(2',3',5'-tri-O-acetyl-beta-d-ribofuranosyl)-2-(pyridinium-1-yl)-9H-purin-6-olate, 1a, exhibits solvent-induced spectral band shifts that are (2)/(3) as large as that of the betaine known as Reichardt's dye, which forms the basis of the E(T)(30) solvent polarity scale. Moreover, the dye 1a is a ribonucleoside and hence has the potential application as a polarity probe for application in RNA oligonucleotides. The isomeric dye 6-(pyridinium-1)-yl-9H-purin-2-olate, 2a, has also been synthesized and exhibits slightly smaller solvatochromic band shifts. The new betaine dyes have also been studied by comparing the experimental and calculated solvatochromic shifts based on the calculation of the UV/vis absorption spectra, using a combination of methods with density functional theory (DFT). The COSMO continuum dielectric method, an applied electric field term in the Hamiltonian, and time-dependent density functional theory (TD-DFT) methods were used to obtain absorption energies, ground-state dipole moments, and the difference dipole moment between the ground and excited states. The calculations predict a lower energy absorption band of charge-transfer character that is highly solvatochromic, and a higher energy absorption band that has pi-pi character which is not solvatochromic, in agreement with the experimental data. For Reichardt's dye the difference dipole moment between the ground and excited state (Deltamu = mu(e) - mu(g)) was also calculated and compared to experiment: Deltamu(calcd) = -6 D and Deltamu(exptl) = -9 +/- 1 D.(1) The ground-state dipole moment was found to be mu(g)(calcd) = 18 D and mu(g)(exptl) = 14.8 +/- 1.2 D.(1).

Variation of spectral, structural, and vibrational properties within the intrinsically fluorescent proteins family: A density functional study

“…In fact, a larger excited-state dipole moment implies that the excited-state energy is more sensitive to the local electrostatic field, which depends on the characteristics of solvents or protein environment. 60 µ increases with the global size of the chromophore, especially when the conjugated tail is present. In fact, in the simplest schematization, µ is a measure both of the charge displacement upon HOMO-LUMO excitation and of the extension of the electronic conjugation across the chromophore, which involves a resonance of π orbitals.…”

Excited States from Time‐Dependent Density Functional Theory

“…113 Several studies include solvent effects, [114][115][116][117][118][119][120][121][122] one example being the behavior of metal ions in explicit water. 123 TDDFT in the realm of linear response can also be used to examine chirality, [124][125][126][127] including calculating both electric and magnetic circular dichroism, 26,[128][129][130][131][132] and it has been applied to both helical aromatics 133 and to artemisinin complexes in solution.…”

Synthesis, spectroscopic (UV–vis and GIAO NMR), crystallographic and theoretical studies of triazine heterocyclic derivatives

“…A large 15 ground-state dipole moment gives rise to strong solvent polarity effects [41,42]. However, we can conclude that the total molecular energies obtained by PCM method decrease with the increasing polarity of the solvent, while the dipole moments and chemical hardness will increase with the increase of the polarity of the solvent for compound 3.…”