Investigating the Thermodynamics of Charge-Transfer Complexes. A Physical Chemistry Experiment

Baum, J. Clayton; Marzzacco, Charles J.; Kendrow, Carolyn

doi:10.1021/ed086p1330

Cited by 11 publications

(8 citation statements)

References 35 publications

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“…If the CT complexes potentially contributing to the absorptivity of BrC were solely intramolecular, their contribution would depend on temperature and solvent but not concentration. From the van't Hoff equation, the equilibrium constant of complexation, which is exothermic, would decrease as temperature increased, and complexes would dissociate, as shown for the well-known chloranil−mesitylene complex 57,58 in Figure S9. Since the potential intramolecular CT complexes in BrC are expected to involve π−π interactions, the enthalpy of formation may be taken as that of the p-benzoquinone− benzene complex (i.e., −7.5 kJ mol −1 in n-heptane 59 ), as assumed previously for CDOM.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

Contribution of Charge-Transfer Complexes to Absorptivity of Primary Brown Carbon Aerosol

Trofimova

Hems

Liu

et al. 2019

ACS Earth Space Chem.

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Light-absorbing organic aerosol, or brown carbon (BrC), has significant but poorly constrained effects on climate. A large fraction of the absorptivity of ambient BrC is unassigned, and organic charge-transfer (CT) complexes have the potential to contribute to this fraction. Here, the contributions of CT complexes to the absorptivity of laboratory-generated BrC and ambient aerosol material influenced by biomass burning have been investigated, using a wide range of chemical, spectroscopic, and physical analyses. Chemical functionalization experiments are inconclusive about the role of CT complexes, whereas fluorescence spectra exhibit distinct spectral features indicative of individual chromophores. Determinations of the concentration and temperature dependences of absorbance are more conclusive. In particular, for laboratory-generated BrC extracted in either water or methanol, absorbance scaled linearly with orders-of-magnitude changes in concentration, indicating that intermolecular complexes do not contribute to the absorptivity. Furthermore, whereas the absorbance of BrC extracts in dimethyl sulfoxide exhibited a slight temperature dependence, consistent with a 15% contribution from intramolecular CT complexes at 15 °C, the complete temperature independence of absorbance of water-soluble extracts from surrogate and ambient BrC indicates a negligible role for CT complexes. Overall, our results find little evidence for CT complexes in the primary BrC studied, suggesting that they do not contribute significantly to the missing absorptivity of ambient BrC.

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Section: ■ Results and Discussionmentioning

confidence: 98%

Contribution of Charge-Transfer Complexes to Absorptivity of Primary Brown Carbon Aerosol

Trofimova

Hems

Liu

et al. 2019

ACS Earth Space Chem.

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“…Besides, CTCs formed by the co-crystallization of two components have been observed to be highly emissive with red-shifted emission via a low-energy singlet 11,12 and triplet CT 13−16 state at room-temperature (RT) and/or 77 K (Figure 1a). In view of these interesting photophysical properties, particularly the existence of a low-energy transition band, CTCs might play an important role in room-temperature red phosphorescence (RTRP) via 3 CT emission. However, most of the reported CTCs are based on multicomponent systems that strongly favor self-aggregation into D or A assemblies alone, rather than complexation between them.…”

Section: Introductionmentioning

confidence: 99%

Room-Temperature Orange-Red Phosphorescence by Way of Intermolecular Charge Transfer in Single-Component Phenoxazine–Quinoline Conjugates and Chemical Sensing

et al. 2018

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Achieving red phosphorescence from purely organic system is a challenging feat due to the predominant thermal nonradiative decay pathways of the excited electrons. Here, we design single-component charge-transfer (CT) complexes based on phenoxazine–quinoline conjugates (PQ1–PQ3), in which the phenoxazine ring is covalently attached to the quinolinyl fragment via a C–N bond. These conjugates in concentration-dependent absorption studies show a new low-energy CT absorption band along with the parent π–π* band with binding constants of up to 102 M–1 due to self-association via intermolecular CT (I2CT). Steady-state emission and phosphorescence decay transient measurements of all of the conjugates in solutions, thin films, and crystals reveal the signature of I2CT that leads to orange-red phosphorescence (ORP) at ambient conditions. Theoretical calculations show the existence of dimer with stronger I2CT characteristics and reduced energy gap between the lowest singlet (S1) and triplet (T1) states (ΔE ST = 0.05–0.14 eV), which is in line with emission measurements. These conjugates are used for solid-state dichloromethane vapor sensors, and PQ3 can be transformed into oxygen sensor. These studies give an insight into the ORP properties and provide a rational strategy for the design of single-component self-CT complexes with ORP feature at ambient conditions.

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“…For this purpose, equilibrium constant was estimated at all samples using spectrophotometer measurements of absorbance using so called "dilution method" (Kendrow et al 2009).…”

Section: Determination Of Thermodynamic Parametersmentioning

confidence: 99%

Influence of casein and different supplements into stability of Corn Oil/Water emulsions

Gandova

Genov

2020

FSAB

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The effects of casein addition in oil-in-water emulsions made with 2 and 4 wt % protein and 10, 15, 25 and 35 wt % corn oil were investigated. A carbohydrate (starch), sodium chloride (NaCl) and potassium chloride (KCl), were used as supplements to prove the emulsion stability. Different analyses were prepared to investigation of emulsions. pH were measured and the values – connected with gravitational creaming and phase separation. Comparing the analyses’ results determined that emulsions prepared with 2 wt % of casein as protein, 25 % of corn oil and mix of carbohydrate 2 % - KCl 2 % exhibit more stability.

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Investigating the Thermodynamics of Charge-Transfer Complexes. A Physical Chemistry Experiment

Cited by 11 publications

References 35 publications

Contribution of Charge-Transfer Complexes to Absorptivity of Primary Brown Carbon Aerosol

Contribution of Charge-Transfer Complexes to Absorptivity of Primary Brown Carbon Aerosol

Room-Temperature Orange-Red Phosphorescence by Way of Intermolecular Charge Transfer in Single-Component Phenoxazine–Quinoline Conjugates and Chemical Sensing

Influence of casein and different supplements into stability of Corn Oil/Water emulsions

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