Dialkylamino fluorescence

Shynkar VV, Klymchenko AS, Piemont E, Demchenko AP, Mely Y (2004) Dynamics of intermolecular hydrogen bonds in the excited states of 4 -dialkylamino-3-hydroxyllavones. On the pathway to an ideal fluorescent hydrogen bonding sensor. J Phys Chem A 108 8151-8159... 

Shynkar VV, Mely Y, Duportail G et al (2003) Picosecond time-resolved fluorescence studies are consistent with reversible excited-state intramolecular proton transfer in 4 -(dialkylamino)-3-hydroxyflavones. J Phys Chem A 107 9522-9529... 

Il ichev YV, Kuhnle W, Zachariasse KA (1998) Intramolecular charge transfer in dual fluorescent 4-(dialkylamino) benzonitriles. Reaction efficiency enhancement by increasing the size of the amino and benzonitrile subunits by alkyl substituents. J Phys Chem A 102(28) 5670-5680... 

Schuddeboom W, Jonker SA, Warman JM, Leinhos U, Kiihnle W, Zachariasse KA (1992) Excited-state dipole moments of dual fluorescent 4-(dialkylamino) benzonitriles. Influence of alkyl chain length and effective solvent polarity. J Phys Chem 96 10809-10819... 

Dialkylamino phthalic acids resulting from the chemiluminescence reaction of 4-dialkylamino-phthalic hydrazides cannot easily form a tris anion because deprotonation of the amino group is impossible. They should therefore not exhibit such a strong decrease in fluorescence efficiency at higher pH values. This can actually be concluded from the pH dependence of the chemiluminescence of the 4-dialkylamino-phthalic hydrazides and related compounds 97>. 

The reaction of 2,2-dimethyl-4,6-dioxo-l,3-dioxane (Meldrum s acid 394) and its analogues with 3-dialkylaminophenols has been used to prepare some fluorescent 7-dialkylamino-4-hydroxycoumarins (Scheme 127) (77M499). The substituted malonic acid (395) or its dehydration product is a possible intermediate, since it is known that diaryl-malonic esters are accessible from phenols and the 1,3-dioxane. 3-Methoxyphenol yields the pyrano[3,2-c]benzopyran-2,5-dione (396) in this reaction, presumably by annelation of another ring on to initially formed 4-hydroxy-7-methoxycoumarin. 

If the amino nitrogen bears several aryl groups as in 2,6-TNS, its donor character is increased, and TICT formation is enhanced, Eqs. (I) and (2). This relation is also found in dyes containing amino groups (see Sect. 4.4) and can explain why Fast Acid Violet, a derivative of Rh-FA shows poor fluorescence with respect to its dialkylamino counterpart Rhodamine 3B (Rh-B). 

Figure 2. Formulas of selected D-A compounds which contain 4-dialkylamino group as an electron donor and reveal dual fluorescence behaviour. Top /)-cyano-A,A-dimethylaniline (I, CDMA) and its model derivatives p-cyano-2,A,A-trimethylaniline (II), p-cyano-2,6,A.A-tetramethylaniline (III, CTMA)./)-aminobenzonitrile (IV, ABN) and l-ethyl-2,3-dihydro-indole-5-carbonitrile (V. BIN). Middle 4-(dimethylamino)pyrimidine (VI), 4-(diethylamino)pyrimidine (VTI), 4-(dimethylamino)-5-methylpyrimidine (VIII), 4-(diethylamino)-5-methylpyrimidine (IX) and 4-(dimethylamino)-pyridine (X). Bottom methyl 4-(dimethylamino)benzoate (XI, DMAMB), ethyl 4-(dimethylamino)benzoate (XII, DMAEB), p-(dimethylamino)-benzaldehyde (XIll) and />-(dimethylamino)acetophenone (XIV).

The present discussion is restricted to D-A molecules which show dual fluorescence in solutions, i.e., 4-dialkylamino derivatives of benzonitrile (I-III, Figure... 

The goal of this work was to show how the fluorescence probe with the general structure I (Scheme 1) behaves in swollen polydimethylsiloxane networks and how the solvation can be examined of linear polydimethylsiloxanes in the presence of covalent bonded probes. This molecule consists of a donor part, e.g., a dialkylamino group, and an acceptor, which is usually an ester group. The following points are important to discuss for a better understanding of the fluorescence behavior... 

Redzimski and Held60 studied 2-(dialkylamino)-9-fluorenol, alkyl = methyl or ethyl (56, 57), as fluorescent probes in several solvents, non-polar, polar and protic. The hypsochromic shifts noted were rather modest. 

Dihexadecyl phosphate (DHP) [2197-63-9] M 546.9, m 75 , pK t 1.2. Recrystallise it from MeOH. Solutions of DHP were made in CHCI3 or CH2CI2 for making vesicles. It has been used for making surfactant vesicles in studies of the viscosity-dependent variations of the fluorescence yield and the polarity induced shift of the emission band maximum F(max) of a derivative of a p-(dialkylamino)benzyUdene]malononitrile [74677-08-0] fluorescence probe. [Lukac JA/w Chem Soc 106 4387 1984]. [Beilstein 1IV 1880 ]... 

Linear PPE-PPV hybrids of the meta and the para varieties (6, 61-64) have been produced by Sonogashira coupling and alkyne metathesis. These polymers show properties that are intermediate between those of the PPVs and the PPEs. Klemm et al. have shown that Horner reactions of suitable substrates lead to linear PPE-PPV hybrids, although the degree of polymerization is not particularly high [98]. The motivation behind these synthetic efforts is to combine the favorable hole injection properties of the PPVs with the blue emission, the stability, and the high fluorescence quantum yields of the PPEs. Several attempts have been made to obtain efficient LED action, but 62, the best one, so far shows a luminance of 147 cd/m at 602 nm, at 14 V, which is not very impressive compared with the numbers that are obtained for PPVs [99-102]. Cross-conjugated PPEs were first synthesized by Bunz et al. (63, 64) and are useful as photodiode-active materials [102]. The dialkylamino substituents in... 

N,N-Dimethylamino)stiIbene (DS), 4-(l-aza-15-Crown-5)stilbene (DS-Crown) and regioselectively bridged 4-(N,N-dialkylamino)stUbene derivatives (DS-B2, DS-B4, DS-B24, DS-B34) have been synthesized and their solvatochromism was measured [31]. In ethanol, the fluorescence quantum yields were obtained at room... 

The substituents may be essential for the chemical reaction of the hydrazide oxidation itself the excitation step may depend on them or they may affect the fluorescence efficiency of the product. It would appear that all three influences are at work both quantitatively and qualitatively. For example, substitution may result in general instability towards oxidation as in the cases of 3,6-diamino- or 3-amino-6-methoxy phthalhydrazide [8]. The ease of oxidation on the chemiluminescent pathway is certainly significant, although it is difficult to separate this from the influence on the population of the excited state. An example of this effect is that of the 4-dialkylamino-phthalhydrazides. Differences in chemiluminescence quantum yields of up to 600-fold were observed, whereas the fluorescence quantum yields of the corresponding 4-dialkyl-amino phthalates only differ by a factor of about 10 [9]. 

Changes in pH affect several properties. One of the most important is the fluorescence efficiency of the product dicarboxylate. The most thoroughly investigated compound 3-aminophthalate (p. 82) has its maximum fluorescence yield at pH 11-11.4 (cf. p. 84). Dialkylamino-substituted phthalic or naphthalene dicarboxylic acid dianions reach their maximum fluorescence yield at a somewhat higher pH [8]. 

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