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Infrared Attenuated Total Reflection Spectroscopy of Surface Active Species
Published in Arthur T. Hubbard, The Handbook of Surface Imaging and Visualization, 2022
Roger P. Sperline, Henry Freiser
ATR is not confined to the infrared. With suitable chromophores (e.g., functionalized aromatic compounds), UV-Vis ATR is possible20 and may be advantageous when there are interferences in the IR. UV-Vis probes, for example, the pyridinium betaine dye Et30, are potentially more sensitive to solvation changes than IR probes. A change in spectral band position with solvent is called “solvatochromism.”
Merits of Selecting Metal-Organic Frameworks as Sensors
Published in Ram K. Gupta, Tahir Rasheed, Tuan Anh Nguyen, Muhammad Bilal, Metal-Organic Frameworks-Based Hybrid Materials for Environmental Sensing and Monitoring, 2022
Harmeet Kaur, Amit L Sharma, Akash Deep
Intramolecular charge transfer (ICT) is the process of tuning emission intensity as well as wavelength through the electron process. Both electron donating and electron accepting groups contribute to ICT. With the presence of both groups on a molecule, dipoles are formed. In the excited state, in the presence of different solvents and operating conditions, the dipole moment varies followed by the change in luminescence. Different environmental contaminants and solvents like toluene, chloroform, isopropanol have been sensed using ICT-based luminescence quenching [34]. Color change is one of the most basic means of sensing any phenomenon. Solvatochromism is the shift in absorption wavelength of material upon change of solvent and the shift is correlated with the polarity of the solvent. Blue shifting of absorption band has been reported in the case of Cu-MOF upon the shift of solvent from low to high polarity (water to chloroform) [35]. Apart from the solvatochromic effect, solvent-dependent color changes in MOF absorption have also been ascribed to changes in coordination environment, for example, change in absorption of Co-MOF upon absorption of different vapors due to change in geometry from octahedral to tetrahedral [35].
Selected Topics
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
A number of poly(arylenevinylene) derivatives have been prepared. Attachment of electron-donating substituents, such as dimethoxy groups (19.3), acts to stabilize the doped cationic form thus lowering the ionization potential. These polymers exhibit both solvatochromism (color change as solvent is changed) and thermochromism (color is temperature dependent).
Ring-chain transformation of 4-aroyl-5-phenylamino-2,3-dihydrothiophene-2,3-diones: Facile and efficient synthesis of novel pyrrolo[2,3-c]pyrazol-3(2H)-ones and 1,2-dihydro-5H,6H-pyridazine-5,6-diones
Published in Journal of Sulfur Chemistry, 2020
Pardis Hafez Taghva, Hassan Kabirifard
The UV-vis absorption spectra of pyrrolo[2,3-c]pyrazol-3(2H)-ones 2a-c and 1,2-dihydro-5H,6H-pyridazine-5,6-diones 3a-d in mentioned solvents display mainly four and three bands, respectively. The absorptions at 230–268 nm can be assigned to the moderate energy transition of the aromatic ring as a excitation while absorptions at 282–321 and 345–391 nm are due to low energy transitions. The absorptions in the range 595–669 nm for 2a-c can be assigned to a highly extended intramolecular charge transfer electronic transition of the azomethine chromophore (Table 1). It is found that the absorption bands generally show bathochromic shifts (positive solvatochromism) as the polarity of solvent was increased. As the data in Table 1 indicates the charge delocalization in 2a-c are more extended than 3a-d. The more polar solvents can stabilize the LUMO orbitals (π*) of 2a-c more than the HOMO orbitals (n) so the excitation energy decreases with increasing solvent polarity.
Synthesis and characterization of novel fluorescent reactive dyes for dyeing of cotton fabrics
Published in The Journal of The Textile Institute, 2022
Maral Pishgar, Kamaladin Gharanjig, Mohammad Esmail Yazdanshenas, Khosro Farizadeh, AboSaeed Rashidi
The polarity of the solvent is the main factor for changing of absorbance band of dyes. Positive solvatochromism corresponds to a bathochromic shift or redshift with increasing solvent polarity. This matter is reliant on the long-lasting dipole moments in the ground and excited state and the dielectric polarization theory (Thiagarajan et al., 2004). Figure 3 showed the relationship between the dielectric constants of solvents and absorbance and an emission wavelength of dyes. Both dyes showed the bathochromic effect in emission and absorption wavelength due to electron density redistribution. This finding was related to the strong interaction between the excited dye molecule and the dipole moment of polar solvent which caused excited form stability (Alaei et al., 2012).
Nano SiO2 catalytic synthesis, NMR spectral studies, photophysical properties and theoretical studies of some styryl imidazole derivatives
Published in Inorganic and Nano-Metal Chemistry, 2022
P. Navamani, K. Jayamoorthy, N. Srinivasan
Stryl imidazoles derivatives were synthesized by using nano SiO2 catalyst and the good efficient of this catalyst is well explained. The luminescence behavior of imidazoles was discussed elaborately with the help of solvatochromic effect in different solvents with varying polarity. Solvatochromic studies imply that the luminescence behavior of the molecule was exceedingly sensitive to the polarity and the protic character of the solvent. From the HOMO-LUMO orbital pictures reveals that HOMO is mostly located on the aniline phenyl ring and the imidazole ring, LUMO is located on the aldehydic phenyl ring. While increasing the solvent polarity, the emission band maxima shifted to the longer wavelength.