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них. Структура всех полученных соединений доказана с помощью ЯМР-спектроскопии, ИЭР-масс-спектрометрии и элементного анализа.
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5. Grykoa D., Grykoa D. T., Sierzputowska-Gracz H., PiaAtekc P., Jurczak J. Factors influencing the course of the macrocyclization of a, ю-diamines with esters of а, ю -dicarboxylic acids // Helvetica Chimica Acta. - 2004. - Vol. 87. - P. 156-166.
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УДК 544.032.732
1 2 1 Stela Minkovska , Todor Deligeorgiev , Slavcho Rakovsky
institute of Catalysis, Bulgarian Academy of Sciences, Acad. Georgy Bonchev St., Bl. 11, 1113, Sofia, Bulgaria 2Sofia University, Chemistry of Faculty,1, James Bourchier Avenue, 1164 Sofia, Bulgaria
SYNTHESIS AND SOLVATOCHROISM OF 1,3,3-TRIMETYLSPIRO[INDOLINO 2,2'-NAPHTHOPYRAN]-10' CARBOXYLIC ACID
A new spiropyran, containing carboxylic group next to the pyranyl O atom, was synthesized in order to evaluate its photocromic and solvatochromic properties. The physical and spectroscopic characteristics (absorption spectra and elemental analysis) of the photochromic compound were determined.
Introduction
The number of investigations on organic photochromic materials has increased considerably in recent years, because of their potential commercial applications including optical filters and devices [1,2], photochromic liquid crystals [3-5], photochromic plastics [6], photochromic substances useful in ophthalmic lenses [7,8], metal complexing agents [9-12] and optical storage discs [13].
Spiropyrans represent an important class of photochromic compounds. They belong to the class of compounds exhibiting both normal and reverse photochromism [14]. The photochromic reactions of these compounds are due to a reversible heterolytic photo-cleavage and rebinding of the pyranyl C (spiro)-O bond, yielding a colored open and colorless closed form as a result. It has been reported that spiropyrans, which posses a coordinating group, next to the pyranyl O atom [15-20], can act as chelating agents in the colored open form. There is no data about synthesis and properties of spyropyran, containing complex formation groups, like -COOH. The aim of this
paper is to present synthesis a new spiropyran derivative containing -COOH group, next to the pyranyl O atom, which is an excellent complex formation ligand.
Experimental
Melting points are determined on a Kofler apparatus and are uncorrected. 1H and 13C spectra NMR were recorded in CDCl3 on a Bruker 250 MHz spectrometer. Absorption spectra are measured on a Specord UV-VIS spectrophotometer (Carl-Zeiss, Jena) in ethanol, acetone, toluene, chloroform and acethonitrile. Used solvents are (p.a.) grade.
Preparation of 2-hydroxy-3 carboxynaphthaldehyde [23]:
0,03 mol of hexamethylenetetramine were added with stirring over 15 min to 0,06 mol of 2-hydroxynaphthalinecarboxylic acid in 20 ml CH3COOH. The mixture was refluxed for 6 hours. The solution was cooled to 60oC, filtered and washed with CH3COOH and then with H2O and the product was dried. Yield = 95 %, m.p. = 250 oC (orange powder)
0.012 mol of the compound obtained in phase I were dissolved in 50 ml 5 % NaOH and boiled under N2 for 3 h until NH3 was evolved. The mixture was cooled to room temperature and 0.04 g of Na2SO3 was added. The acidified solution (pH =1-2) was filtered by 0 oC and the precipitate was washed with cool 2N HCl, then with H2O and dried. Yield = 90 %, (m.p. = 211O (yellow powder)
Preparation of 1,3,3-trimethylspiro[indoline2,2-naphthopyran]-10'carboxylic acid: 0.01 mol of 2-hydroxy - naphthalenecarboxyaldehyde was refluxed in 50 ml C2H5OH and to the hot solution was added drop wise over 15 min a solution of 0,011 mol 1,3,3 - trimethyl-2-methylene indoline in 10 ml C2H5OH. The mixture then refluxed for 1 hour and cooled until the precipitate as formed. After standing for some time, the precipitated product was filtered by suction and washed with ethanol. The product was purified by recrystalization in ethanol.
Characterization data, yield, m.p., absorption and elemental analysis are shown in Table 1. NMR spectra of dye 6 7.22-8.89 (m 11H, Ar) 1.86 (s 6H, 2xCH3) 3.76 (s, 3H, N+-CH3) 11 ppm 13C CDCl3
C-i C-2 C-3 C-4 C-5 C-6 C-7 C-8 C-9 C-10 C-11 C-12
116.1 125.4 131.7 141.3 iii.i 126.1 49.7 28.9 28.9 31.8 104.8 128.9
C-13 C-14 C-15 C-16 C-17 C-18 C-19 C-20 C-21 C-22 C-23 C-24
130.7 119.9 169.2 122.2 123.7 121.9 144.2 142.2 147.4 137.3 179.2 180.7
Table 1. Characterization data for dye 6
Yield % of purified product (reaction time, h) m. p. (oC) X max (nm) merocyanine (ethanol) Molecular formula Analysis % found/calc. C H N
75 (1) 240 - 242 585 C24H21NO3 77.63 5.66 3.77 77.48 5.94 4.43
Results and discussion
The general route to spiropyran involves formulation of the appropriate phenol or derivative, followed by condensation of the obtained ortho-hydroxybenzaldehyde with 1,3,3-trimethyl-2-methyleneindoline (Fisher s base) in absolute ethanol [21].
Nucleophilic attack by Fisher's base on the carbonyl group gives an aldol product, which undergoes dehydration followed by ring closure. However, condensation of Fisher s base with ortho-hydroxybenzaldehydes does not always give the spiropyran. The obtainment of other products are also possible (e.g. a merocyanine or a tricyclic compound) depending on the substituent groups in the aldehyde. Ortho-hydroxyformylnaphthaldehyde derivatives are almost invariably prepared by direct formulation of the corresponding hydroxyl compound. The route of choice depends of:
i. compatibility of the various reaction conditions ;
ii. the present of other substituents in the starting hydroxyl compound
iii. substituents in position other than ortho to the hydroxyl group.
The method used to prepare the present compound was a reaction of hexamethylene tetramine with paraformaldehyde in acid solution (modified Duff reaction) to give 4 in Scheme 1.
CH=N-CH2-N = ÇH
2
V/KX-COOH
N4(CH2)6 ->■
CH3COOH t= 100oC
COOH HOOC 2
1
NaOH
2
t
COOH
Na2SO3
+ CH2O + NH3 -2
HCl (pH=1-2)
CHO
OH
COOH
SCHEME 1
The photochromic compound (6) was synthesized by a direct condensation of (4) with 1,3,3-trimethyl-2-methyleneindolenine (Fisher s base) (5) in absolute C2H5OH (Scheme 2).
CHO
H3C
N I
CH3 5
C2H5OH
SCHEME 2
H3C
HOOC 6
H3Q8 9
CH
^ 13 16 17
14 15/ \
/20 19
22 21
18
Characterization data of the synthesized dye are given in Table 1. The compound is colored in goldgreenish in the solid state after recrystalization from ethanol. The compound (6) is well soluble in acetone, acetonitrile, toluene, chloroform and ethanol and insoluble in aliphatic solvents such as heptane and hexane. The absorption spectra of 1.10-5M solution of 1,3,3 trimethylspiro[indolino 2,2-naphthopyran]-10 carboxylic acid (6) in different solvents are given in Fig 1. In the investigated solvents the compound exhibits two forms - opened
4
3
o
t
2
4
1
6
merocyanine form (Xmax = 585 nm in ethanol and 590 nm in toluene) and the closed spiropyrane form (Xmax = 380 nm in both ethanol and acetone and 355 nm in toluene).
Fig. 1. Absorption spectra of 1,3,3-trimethylspiro [indolino 2,2 -naphthopyran]-10 carboxylic acid (6) 1.10-
5M in acetone (1), ethanol (3) and toluene (3)
It was found that after treating the ethanol solution of the dye with buffer pH = 9 the
red violet colour of the solution becomes reversibly colorless (Fig. 2).
2
1.2
1.0
0.8
0.6
0.4
0.2
0.0 50
x 1000 cm
Fig. 2. Absorption spectra of 1,3,3-trimethylspiro [indolino 2,2 -naphthopyran]-10 carboxylic acid (6) in
ethanol (1) by pH =5 and (2) by pH = 7
According to [22] the probable merocyanine form of the synthesized photochromic compound appears to give chelate complexes with transition metal ions as Cr3+, Co2+, Cu2+, Ni2+ and Fe3+. This study is in progress.
CONCLUSIONS
A new spiropyran, containing carboxylic group next to the pyranyl "O" atom was synthesized. The photochromic and solvatochromic properties were investigated. The physical and spectroscopic characteristics were determined.
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