Effect of the aggregate state on the conjugation in the 2-(2?-quinolyl)benzoxazole system

Klyuev, N. A.; Kurapov, P. B.; Александров, Г. Г.; Грандберг, И. И.

doi:10.1007/bf00506148

Cited by 1 publication

(6 citation statements)

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“…Among them, the largest delocalization over 2-QBO in β than the others can be easily found. This orbital character directly leads to the lowest LUMO energy in β (Table ), which is consistent with the best planarity of the 2-QBO ligand in β . On the other hand, the HOMO in each polymorph is mainly a M–L antibonding orbital and shows its contribution from the Cu(I) d orbital and the P p orbital mixed with a little p orbital of phenyl group from the PPh 3 ligand.…”

Section: Resultssupporting

confidence: 75%

“…The comparison of the three cationic species reveals an obvious difference in the dihedral angle (θ) between benzoxazolyl and the quinolyl group of the 2-QBO ligand. In α phase, the entire 2-QBO ligand presents an obvious flip with the θ value being 15.169(60)°, while the angles of the other two phases are 4.170(32)° (β1), 0.309(57)° (β2), and 9.284(45)° (γ), showing a sequence of α > γ > β. Klyuev and co-workers previously suggested that the magnitude of the θ value may depend on the temperature and polarity of the solvent . In this case, the magnitude of the θ value is strongly associated with the employed temperature and the polarity of the processing solvent ( E T N ).…”

Section: Resultsmentioning

confidence: 97%

“…All reagents were purchased as analytical grade and used as received, except that the ligand 2-(2′-quinolyl)benzoxazole (2-QBO) was synthesized according to a literature method reported previously. 9 All solvents were commercially available and used without additional purification. The solvothermal reaction was performed by using a 25 mL Teflon-line stainless steel autoclave under autogenous pressure to grow crystals for single-crystal X-ray diffraction.…”

Section: Methodsmentioning

confidence: 99%

Section: Experimental Sectionmentioning

confidence: 99%

“…In α phase, the entire 2-QBO ligand presents an obvious flip with the θ value being 15.169(60)°, while the angles of the other two phases are 4.170(32)°(β1), 0.309(57)°(β2), and 9.284(45)°(γ), showing a sequence of α > γ > β. Klyuev and co-workers previously suggested that the magnitude of the θ value may depend on the temperature and polarity of the solvent. 9 In this case, the magnitude of the θ value is strongly associated with the employed temperature and the polarity of the processing solvent (E T N ). Thus, a mechanism can be proposed that the changes of the temperature and E T N value lead to the conformational isomerism of 2-QBO and, consequently, result in the formation of three isomeric complexes with variable E T , μ, and tetrahedral coordination geometry.…”

Section: Crystal Structuresmentioning

confidence: 99%

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Three Reversible Polymorphic Copper(I) Complexes Triggered by Ligand Conformation: Insights into Polymorphic Crystal Habit and Luminescent Properties

et al. 2015

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Three luminescent polymorphs based on a new copper(I) complex Cu(2-QBO)(PPh3)PF6 (1, PPh3 = triphenylphosphine, 2-QBO = 2-(2'-quinolyl)benzoxazole) have been synthesized and characterized by FT-IR, UV-vis, elemental analyses, and single-crystal X-ray diffraction analyses. Each polymorph can reversibly convert from one to another through appropriate procedures. Interestingly, such interconversion can be distinguished by their intrinsic crystal morphologies and colors (namely α, dark yellow plate, β, orange block, γ, light yellow needle) as well as photoluminescent (PL) properties. X-ray crystal structure analyses of these three polymorphs show three different supramolecular structures from 1D to 3D, which are expected to be responsible for the formation of three different crystal morphologies such as needle, plate, and block. Combination of the experimental data with DFT calculations on these three polymorphs reveals that the polymorphic interconversion is triggered by the conformation isomerization of the 2-QBO ligand and can be successfully controlled by the polarity of the process solvents (affecting the molecular dipole moment) and thermodynamics (affecting the molecular total energy). It is also found that the different crystal colors of polymorphs and their PL properties are derived from different θ values (dihedral angle between benzoxazolyl and quinolyl group of the 2-QBO ligand) and P-Cu-P angles based on TD-DFT calculations. Moreover, an interesting phase interconversion between γ and β has also been found under different temperature, and this result is consistent with the DFT calculations in which the total energy of β is larger than that of γ. This polymorphism provides a good model to study the relationship between the structure and the physical properties in luminescent copper(I) complexes as well as some profound insights into their PL properties.

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Section: Resultssupporting

confidence: 75%

Section: Resultsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Section: Experimental Sectionmentioning

confidence: 99%

Section: Crystal Structuresmentioning

confidence: 99%

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