Clip-like arrangements of molecules in the cocrystals of phenazine with hydroxy-aromatics in their respective self-assemblies and photophysical properties were presented. Phenazine cocrystals with 1,2dihydroxybenzene provided assembly with butterfly-like arrangements. In these cocrystals, the phenazine molecules occurred in parallel pairs having extensive p-stacking. The clip-like cocrystals with 1,3-dihydroxybenzene also exhibited parallel pairs of phenazine molecules that were parallel cofacial pstacked. The hydrated cocrystals of phenazine with 1,2,3-trihydroxybenzene had chains of parallel cofacial phenazine rings having three distinguishable p-separation distances among the centroids of the phenazine rings. Also, 2,7-dihydroxynaphthalene formed a clip-like cocrystal with phenazine, which encapsulated an additional molecule of phenazine. This cocrystal also provided chain-like parallel arrangements of the phenazine molecules. The emission and quantum yields of the cocrystals were determined by the integrating sphere method, which indicated that only the cocrystal of phenazine with 2,7-dihydroxynaphthalene showed monomer-like emission of phenazine and the rest of the cocrystals were in a quenched state. In the solution phase, quenching of the emission of hydroxynaphthalene was observed when phenazine was added to an independent solution of 2,7-dihydroxynaphthalene or another hydroxynaphthalene. However, when hydroxybenzenes were added to a solution of phenazine, fluorescence enhancements of phenazine occurred due to photo-electron transfer. Fig. 1 (a) Some possible hydrogen-bonded assemblies of phenazine with aromatic diols and (b) structures of phenazine and different organic aromatic diols used in this study.33404 | RSC Adv., 2019,9,[33403][33404][33405][33406][33407][33408][33409][33410][33411][33412] This journal is
Positional
isomers of zinc–nitrobenzoate complexes possessing
pyridine -3-(or-4-) carboxamide are used for a comparative theoretical
and experimental study to understand their utility as model complexes
to understand the role of metal-to-ligand charge transfer in aggregation-induced
emission (AIE). Among the five different model zinc complexes, four
of them are non-ionic, and one is an ionic complex. The frontier molecular
energy levels of different combinations of the positional isomeric
complexes and the absorption maximum were ascertained by density functional
theory calculations. The PolyQ value obtained from solid samples of
each complex is different. Shifts in the emissions to higher wavelengths
than the expected emission for the S1 to S0 transition
were observed due to aggregations. The highest value of PolyQ among
the complexes was 13.56% observed for emission at 439 nm (λex = 350) of the non-ionic complex, namely, (di-aqua)bis(pyridine-3-carboxamide)di(2-nitrobenzoato)zinc(II)
monohydrate. Close resemblance in emission lifetime decay profiles
of the solid samples of those complexes and the respective solutions
of those complexes in dimethyl sulfoxide with or without water showed
a common trend, suggesting aggregation-induced emission in each case.
Aggregation-induced emission caused by adding water in dimethyl sulfoxide
solution of each complex showed an initial increase without a shift
in the emission wavelength followed by a quenching with a shift of
the respective emission peak to a short wavelength. Dynamic light
scattering studies showed an increase in the average particle sizes
upon an increase in the concentration of water. This indicated initial
participation of water molecules to form aggregates with the complexes,
favoring an increase in the AIE intensity. Aggregation of each complex
changes with the concentration of water, and an increase in the concentration
of water beyond a characteristic limit causes lowering of the emission
intensity to the short wavelength.
Five dicarboxylate coordination polymers having 1-phenyl-3-((pyridin-4-yl)methyl)urea (L) as co-ligands with general formula [M2L2(dicarb)(H2O)2]n (dicarb = succinate or fumarate for M = Co and Zn; terephthalate for M = Co) were...
The structural characterisation of self-assemblies and photoluminescence of the perchlorate salts of the 1-(naphthalen-1-yl)-3-(pyridin-4-ylmethyl)urea (naphurea) and 1-(naphthalen-1-yl)-3-(pyridin-4-ylmethyl)thiourea (naphthiourea) and their comparision with the parent urea or thiourea derivatives are presented....
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