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Solvatochromism of 1-(p-Aminostyryl)pyridium Salts

100%

Gawinecki R. , Trzebiatowska K.

2001

tom Vol. 75, nr 2

231-239

Solvatochromism of eighteen 1-methyl-(p-aminostyryl)pyridinium perchlorates was studied. For each solvent the V~ max values follow the R o substituent constants of the amino groups present in the molecule. The V~ max values for compounds are usually highest and lowest in water and in methylene chloride, respectively. The substituent bathochromic shifts in some solvents are as large as 5700 cm-1. No inverted solvatochromism is observed. Analysis of the spectra do not confirm also this effect to be negative. Dependence between the band position and solvent polarity, hydrogen bond donor acidity and hydrogen bond acceptor basicity is of low quality. There is no simple relationship between the V~ max values and the solvent dielectric constants.

Synthesis and Solvatochromism of 2-(N-Pyridinio)-pyrimidin-4-olate and related Betaines Derived from Uracils

100%

Wenska G. , Insińska M. , Skalski B.

tom Vol. 74, nr 5

659-671

Excited-state Solvation of Rhodamines: Dielectric and Specific Contributions

100%

Ferreira J. A. B. , Costa S. M. B.

2008

tom Vol. 82, nr 4

893-899

Primary to tertiary amine based compounds of the form 9'-(2-ester-carbonyl)-phenyl- 3',6'-bis-(amino)-xanthylium) are studied as models for this class of compounds as regards the S1S0 shifts in solution. The magnitude of the solvatochromic shift decreases from primary amine to tertiary amine rhodamine chromophore. Primary aminoxanthylium spectral energy at maximum absorption decreases with the solvent electronic polarization whilst it increases with the orientational polarization function, suggesting extensive reorientation in the dipolar moment upon S1S0 excitation. By contrast, upon electronic excitation smaller dipolar moment variations are found in N-alkyl rhodamines, respectively with secondary and tertiary amine groups. Primary and secondary amine rhodamines' NH groups establish strong interactions with electron rich atomic centers of solvent molecules increasing the electronic stabilization energy.

Electrophilic Substitution in 5,6-Bis(dimethylamino)acenaphthylene as a Route to Push-Pull Proton Sponges

88%

Mekh M. A. , Pozharskii A. F. , Ozeryanskii V. A.

2009

tom Vol. 83, nr 9

1609-1621

Unlike 1,8-bis(dimethylamino)naphthalene (pro ton sponge), 5,6-bis(dimethyl - amino)acenaphthylene 2 has been shown to undergo H/D-ex change in CF3CO2D at 65°C. Both hydrogen atoms at the C1=C2 double bond and inpositions 3(8) and 4(7) of the naphthalene fragment are reactive in the ratio 3:1.3:1, respectively. Arylsulfonation and nitration of 2 with tetranitromethane provide direct substitution at C(1) with the formation of push-pull derivatives in moderate yield. Isomeric 3-ni tro- and 4-ni tro- 5,6-bis(dimethylamino)acenaphthylenes can be synthesized via dehydrogenation of their more accessible acenaphthene precursors. The Vilsmeier formylation of 2 affords along with 1-formyl- and 1,2-diformyl derivatives some amount of 1,7-dialdehyde that reflects a comparable reactivity of ethylene and naphthalene moieties in the non-protonated substrate. The green ish-yel low proton salt of deep violet 5,6-bis(dimethyl amino)acena -phthylene-1,2-dicarbaldehyde has been found to exhibit strong positive solvatochromism caused by partial deprotonation.

Solwatochromia i barwniki solwatochromowe

75%

Wróblewska E. K. , Soroka J. A. , Soroka K. B.

Wiadomości Chemiczne

2002

tom [Z] 56, 1-2

113--150

The phenomenon of solvatochromism is presented, taking into account the constitution of solvatochromic dyes, the physical interpretation and mathematical description (models) of solute-solvent interaction. The discussion covers Onsager's early reactions field model and subseqent qualitative interpretation of the solvent effect on solute dipole moment change by Bayliss and McRea. Subsequently solvatochromic dyes were presented briefly as empirical polarity indicators with respect to other methods applied to this goal. Binary solvents mixtures polarity models were critically discussed, taking into account the conceptions of Langhals, Dawber, Bosh and Rosés and Skwierczyński and Connors. After this introduction Soroka's models were presented: the physicochemical V-B-HB model based on solute electronic structural changes in pure solvents and the SA-SAB-SB model of solvatochromism in binary solvent mixtures. Both models describe well the behaviour of many pure solvents, as well as the properties of a number of binary systems series including ones well known from textbooks. These models provide reliable support for advanced investigations and precise interpretation of molecular interactions in liquids.