Novel stilbene-triazine symmetrical optical brighteners: Synthesis and applications

J Fluoresc

DOI 10.1007/s10895-014-1392-1

ORIGINAL PAPER

Novel Stilbene-triazine Symmetrical Optical Brighteners:

Synthesis and Applications

Aamer Saeed & Ghulam Shabir & Iram Batool

Received: 1 February 2014 /Accepted: 7 April 2014

#

Springer Science+Business Media New York 2014

Abstract A series of new high light fastness, hot pressing

fastness optical brighteners was efficiently synthesized by a

three-step approach involving the successive replacement of

the three chloro groups of 2,4,6-trichloro-1,3,5-triazine under

different conditions of temperature and pH. Thus, 2,4,6-

trichloro-1,3,5-triazine was treated with different anilines

and the resulting dichlorotriazinyl intermediates (3a-I) were

further condensed with 4,4-diaminostilbene-2,2′-disulfonic

acid to afford bis-monochlorotriazine (5a-I) followed by nu-

cleophilic substitution with ethanolamine to furnish the final

hybrid brighteners (7a-I). All of the newly synthesized com-

pounds were characterized by Fourier-Transform Infrared

(FT-IR), UV-visible absorption, NMR spectroscopy and the

elemental analyses. The synthesized optical brighteners were

also assessed for their efficacy as fluorescent brightening

agents.

number of applications in diverse fields. These are commonly

used in the HYP-containing pulp also known as bleached

chemi-thermo mechanical pulps (BCTMP) and paper industry

is to increase their whiteness and brightness stability; in cos-

metics and to increase the visibility of fabrics and in night

vision devices [1]. Brighteners are also added to laundry

soaps, detergents, or cleaning agents, where they adsorb to

fabrics or materials during the washing or cleaning process

and when illuminated by ultraviolet light they fluoresce and

fabrics appear brighter [2].

Brighteners are highly susceptible to adsorption. They are

removed from surface and ground water by adsorption onto

soil and organic material. They operate through the process of

fluorescence. They absorb invisible ultraviolet (UV) radiation

at wavelengths below 400 nm and through an electrophysical

change, emit light mostly in the blue end of the visible

spectrum at about 400–450 nm [3]. Optical brighteners have

been used in experimental mycology for quantization of fun-

gal cells or studying cell wall architecture but most important,

brighteners are used in histopathology of mycosis in derma-

tology and diagnosing pneumocystosis. Another conceivable

feature of the brighteners in medical mycology is their poten-

tial use as homing agents for systemically applied antifungals.

This may be particularly effective with those antifungals that

act on the cell wall as is the case with the candins [4].

In additions to coumarins, imidazolines, diazoles,

triazoles, benzoxazolines and biphenyl-stilbenes; 4,4′-

bis-(triazinylamino) stilbene-2,2′-disulfonate derivatives

are one of the important classes of OBAs. These are

widely used to create intense and bright white shades

in textiles, pulps and papers, and are additives to laundry

detergents [5]. Triazine-stilbene compounds showed a

high degree of whiteness with moderate UV blocking

properties [6]. It has been shown that stilbene optical

brighteners could enhance the biological activities of

NPVs against pests like the tobacco budworm, Heliothis

.

Keywords Optical brightening agents (OBAs) UV-visible

.

spectra Fastness properties

Introduction

Optical brightening agents (OBA) have become an integral

part of our everyday life and culture; finding an increasing

Electronic supplementary material The online version of this article

(doi:10.1007/s10895-014-1392-1) contains supplementary material,

which is available to authorized users.

:

A. Saeed (*) G. Shabir I. Batool

Department of Chemistry, Quaid-I-Azam University,

Islamabad 45320, Pakistan

e-mail: asaeed@qau.edu.pk

A. Saeed

e-mail: aamersaeed@yahoo.com

J Fluoresc

virescens. These studies served to highlight the potential

usefulness of stilbene brighteners with insect pathogenic

viruses to control insect pest populations [7].

To a vigorously stirred aqueous solution of 4,4-

diaminostilbenedisulfonic acid (4) (0.001 mol) maintained at

pH 6.5 was added intermediates (3a-I) and the resulting

solution stirred for 4 h at 40–45 °C to afford the bis-

monochlorotriazine products (5a-I).

Third condensation with ethanolamine (6) (0.002 mol) and

(5a-I) was achieved by heating the reaction mixture at 90–

95 °C for 3 h at pH 9. On completion, the reaction mixture was

rotary evaporated to afford the OBAs (7a-I) as the solid

products [10].

Fluorescent brighteners having antioxidant properties have

been synthesized from 4,4′-bis-(triazin-6-yl) diamino stilbene-

2,2′-disulfonate on condensation with cyanuric chloride and

the phenol derivatives, 4-amino-2,6-di-tert-butylphenol and 4-

(2-aminoethyl)-2,6-di-tertbutyl phenol. Phenolic antioxidants

form the stable low-energy radical by the stable resonance

hybrids to prevent further oxidation. However, these deriva-

tives have shown lesser color fastness and whiteness as evi-

denced from their application results on cotton fibers in com-

parisonwithstandardfluorescentbrightenersC186andC190

[8].

Herein, we wish to report the synthesis of a small

library of new triazine derivatives of 4,4′-bis-(1,3,5-

triazinylamino)stilbene-2,2-disulfonate and evaluation of

their performance by light fastness, chlorinated water

fastness, washing fastness and CIE (International Com-

mission on Illumination) Whiteness Index measurement.

Sulfanilic Acid Derivative of OBA. (7a)

(7a) was prepared according to the general procedure using

sodium 4-aminobenzenesulfonate, cyanuric chloride, sodium

lauryl sulfate, 4,4-diaminostilbene-disulfonic acid. Mol.Wt:

1078, Yield 84 %; UV-max/nm, (de-ionized water) 461 nm;

IR (KBr): 3419 (N-H), 1646 (C=C), 1589, 1412 (C=C, Ar),

1367 (-CH₃), 1302 (C-N), 1088 (S=O), 989 (=C-H, bend),

1

827 (S-O). HNMR (300 MHz, DMSO-d₆): δ 3.05 (t, 2H,

CH₂), 3.45 (t, 1H, OH), 3.72 (t, 2H, CH₂), 6.92 (d, 2H, J=

7.48, Ar-H), 7.06 (d, 2H, J=7.78 Hz, CH=CH), 7.13 (s, 1H,

Ar-H), 7.42 (d, 2H, J=7.22, Ar-H), 7.63 (d, 2H, J=5.96 Hz,

Ar-H), 10.14 (br. s, 6H, NH). Anal. Calcd for

C₃₆H₃₄N₁₂Na₄O₁₄S₄: C, 40.07; H, 3.18; N, 15.58; S, 11.89.

Found: C, 40.02; H, 3.20; N, 15.60; S, 11.91.

Experimental

General

All solvents and reagents were purchased from commercial

sources and used as received. NMR spectra were recorded in

DMSO-d₆by using Bruker AC 300 MHz for H NMR and

5-Nitro-2-(4-nitrophenylamino)benzenesulfonic Acid

Derivative of OBA. (7b)

1

75 MHz for ¹³C NMR Splitting patterns were as follows: s

(singlet), d (doublet), dd, (double doublet), t (triplet), m

(multiplet) and br (broad). Chemical shifts are reported in δ

(ppm) and coupling constants are given in Hertz (Hz). UV/

visible absorption spectra were recorded on a Perkin Elmer,

L50 Spectrofluorimeter. FT-IR spectra were taken in KBr

pellets on a Bruker EQUIOX-55 FT-IR spectrometer.

(7b) was prepared according to the general procedure using 5-

nitro-2-(4-nitrophenylamino) benzenesulfonic acid. Mol.Wt:

1304, Yield 86 %; UV-max/nm, (de-ionized water) 457 nm;

IR (KBr): 3430 (N-H), 1651 (C=C), 1592, 1413 (C=C, Ar),

1584 (C=N), 1488 (N-H), 1360 (-CH₃), 1302 (C-N), 1089

1

(S=O), 825 (S-O), 985 (=C-H, bend). HNMR (300 MHz,

DMSO-d₆): δ 3.15 (t, 2H, CH₂), 3.44 (t, 1H, OH), 3.73 (t, 2H,

CH₂), 6.46–7.98 (Ar-H), 7.07 (d, 2H, J=7.76 Hz, CH=CH),

10.21 (br. s, 6H, NH). Anal. Calcd for C₄₈H₄₂N₁₆Na₂O₁₈S₄:

C, 44.17; H, 3.24; N, 17.17; S, 9.83. Found: C, 44.12; H, 3.22;

N, 17.20; S, 9.86.

Preparation of Erlich’s Reagent

Ehrlich’s reagent is prepared by dissolving 2.0 g of p-

dimethylaminobenzaldehyde (DMAB) in 50 mL of 95 %

ethanol and 50 mL of concentrated hydrochloric acid. It is

freshly prepared according to literature procedure [9].

2-Amino-5-(4-aminophenylamino)benzenesulfonic Acid

Derivative of OBA. (7c)

General Procedure for the Synthesis of Optical Brighteners

(7c) was prepared according to the general procedure using 2-

amino-5-(4-aminophenylamino) benzenesulfonic acid.

Mol.Wt: 1244, Yield 89 %; UV-max/nm, (de-ionized water)

459 nm: IR (KBr): 3418 (N-H), 1644 (C=C), 1582, 1411

(C=C, Ar), 1558 (C=N), 1434 (N-H), 1359 (-CH₃), 1302

(C-N), 1072 (S=O), 828 (S-O), 982 (=C-H, bend). ¹HNMR

(300 MHz, DMSO-d₆): δ 3.07 (t, 2H, CH₂), 3.45 (t, 1H, OH),

3.71 (t, 2H, CH₂), 5.99 (s, 2H, NH₂), 6.22–7.48 (Ar-H),

To a well stirred aqueous solution of cyanuric chloride (1)

(0.38 g, 0.002 mol) in ice bath at 4°–5 °C was added of

sodium lauryl sulfate (0.01 g) and stirred to a fine suspension.

To this suspension was added a solution of substituted anilines

(2a-I) (0.002 mol) at 5 °C and 2–2.5 pH. Condensation was

completed after 3 h as checked by Erlich’s reagent to yield the

mono condensation bis-dichlorotriazinyl products (3a-I).

J Fluoresc

7.05 (d, 2H, J=7.77 Hz, CH=CH), 10.32 (br. s, 8H, NH).

Anal. Calcd for C₄₈H₄₆N₁₆Na₂O₁₄S₄: C, 46.30; H, 3.72; N,

18.00; S, 10.30. Found: C, 46.25; H, 3.69; N, 18.04; S, 10.35.

(=C-H, bend). ¹HNMR (300 MHz, DMSO-d₆): δ 3.06

(t, 2H, CH₂), 3.45 (t, 1H, OH), 3.73 (t, 2H, CH₂), 6.28–7.44

(Ar-H), 7.01 (d, 2H, J=7.73 Hz, CH=CH), 10.35 (br. s, 6H,

NH). Anal. Calcd for C₃₆H₃₀N₁₂Na₂O₈S₂Cl₄: C, 42.78; H,

2.99; N, 16.63; S, 6.35. Found: C, 42.72; H, 3.01; N, 16.59; S,

6.38.

2-Aminothiazole Derivative of OBA. (7d)

(7d) was prepared according to the general procedure using 2-

aminothiazole. Mol.Wt: 886, Yield 82 %; UV-max/nm, (de-

ionized water) 461 nm; IR (KBr): 3479 (N-H), 1646 (C=C),

1593, 1404 (C=C, Ar), 1584 (C=N), 1489 (N-H), 1394

(-CH₃), 1320 (C-N), 1088 (S=O), 827 (S-O), 989 (=C-

H, bend) ¹HNMR (300 MHz, DMSO-d₆): δ 3.04 (t, 2H, CH₂),

3.45 (t, 1H, OH), 3.75 (t, 2H, CH₂), 6.55 (d, 2H, J=7.48, H-

tiazole), 7.05 (d, 2H, J=7.76 Hz, CH=CH), 7.52 (d, 2H, J=

5.96 Hz, H-tiazole), 7.13 (s, 1H, Ar-H), 7.42 (d, 2H, J=7.22,

Ar-H), 10.31(br. s, 6H, NH). Anal. Calcd for

C₃₀H₂₈N₁₄Na₂O₈S₄: C, 40.63; H, 3.18; N, 22.11; S, 14.46.

Found: C, 40.59; H, 3.15; N, 22.15; S, 14.49.

2,4-Dichloroaniline Derivative of OBA. (7h)

(7h) was prepared according to the general procedure using

2,4-dichloroaniline. Mol.Wt: 1010, Yield 83 %; UV-max/nm,

(de-ionized water) 461 nm; IR (KBr): 3418 (N-H), 1650

(C=C), 1587, 1409 (C=C, Ar), 1587 (C=N), 1485 (N-H),

1358 (-CH₃), 1302 (C-N), 1088 (S=O), 828 (S-O), 984 (=C-

1

H, bend). HNMR (300 MHz, DMSO-d₆): δ 3.04 (t, 2H,

CH₂), 3.45 (t, 1H, OH), 3.71 (t, 2H, CH₂), 6.32–7.43

(Ar-H), 7.02 (d, 2H, J=7.75 Hz, CH=CH), 10.17 (br. s,

6H, NH). Anal. Calcd for C₃₆H₃₀N₁₂Na₂O₈S₂Cl₄: C, 42.78;

H, 2.99; N, 16.63; S, 6.35. Found: C, 42.75; H, 3.00; N, 16.67;

12.64; S, 6.39.

3-Flouroaniline Derivative of OBA. (7e)

(7e) was prepared according to the general procedure using 3-

flouroaniline. Mol.Wt: 908, Yield 89 %; UV-max/nm, (de-

ionized water) 460 nm; IR (KBr): 3419 (N-H), 1646 (C=C),

1575, 1412 (C=C, Ar), 1525 (C=N), 1488 (N-H), 1367

(-CH₃), 1259 (C-N), 1088 (S=O), 855 (S-O), 996 (=C-

H, bend). ¹HNMR (300 MHz, DMSO-d₆): δ 3.01 (t, 2H,

CH₂), 3.45 (t, 1H, OH), 3.78 (t, 2H, CH₂), 6.15–7.43 (Ar-H),

7.08 (d, 2H, J=7.79 Hz, CH=CH), 10.24 (br. s, 6H, NH).

Anal. Calcd for C₃₆H₃₂N₁₂Na₂O₈S₂F₂: C, 47.58; H, 3.55; S,

7.06. Found: C, 47.63; H, 3.49; S, 7.08.

2,6-Dibromo-4-flouroaniline Derivative of OBA. (7i)

(7i) was prepared according to the general procedure using

2,6-dibromo-4-flouroaniline. Mol.Wt: 1224, Yield 90 %; UV-

max/nm, (de-ionized water) 460 nm; IR (KBr): 3393 (N-H),

1644 (C=C), 1590, 1411 (C=C, Ar), 1584 (C=N), 1489 (N-H),

1326 (-CH₃), 1302 (C-N), 1087 (S=O), 823 (S-O), 989 (=C-

1

H, bend). HNMR (300 MHz, DMSO-d₆): δ 3.02 (t, 2H,

CH₂), 3.45 (t, 1H, OH), 3.74 (t, 2H, CH₂), 6.82–7.45

(Ar-H), 7.03 (d, 2H, J=7.76 Hz, CH=CH), 10.15 (br. s, 6H,

NH). Anal. Calcd for C₃₆H₂₈N₁₂Na₂O₈S₂Br₄F₂: C, 35.31; H,

2.30; N, 13.73; S, 3.00. Found: C, 35.27; H, 2.32; N, 13.69; S,

3.02.

2,5-Dichloroaniline Derivative of OBA. (7f)

(7f) was prepared according to the general procedure using

2,5-dichloroaniline. Mol.Wt: 1010, Yield 86 %; UV-max/nm,

(de-ionized water) 459 nm; IR (KBr): 3420 (N-H), 1645

(C=C), 1568, 1410 (C=C, Ar), 1519 (C=N), 1488 (N-H),

1361 (-CH₃), 1302 (C-N), 1089 (S=O), 826 (S-O), 986 (=C-

2,6-Dinitroaniline Derivative of OBA. (7j)

(7j) was prepared according to the general procedure using

2,6-dinitroaniline. Mol.Wt: 1052, Yield 85 %; UV-max/nm,

(de-ionized water) 460 nm; IR (KBr): 3419 (N-H), 1644

(C=C), 1588, 1411 (C=C, Ar), 1584 (C=N), 1487 (N-H),

1358 (-CH₃), 1302 (C-N), 1087 (S=O), 824 (S-O), 983 (=C-

1

H, bend). HNMR (300 MHz, DMSO-d₆): δ 3.07 (t, 2H,

CH₂), 3.45 (t, 1H, OH), 3.69 (t, 2H, CH₂), 6.40–7.45

(Ar-H), 7.04 (d, 2H, J=7.75 Hz, CH=CH), 10.39 (br. s, 6H,

NH). Anal. Calcd for C₃₆H₃₀N₁₂Na₂O₈S₂Cl₄: C, 42.78; H,

2.99; N, 16.63S, 6.35. Found: C, 42.73; H, 3.02; N, 16.58; S,

6.38.

1

H, bend). HNMR (300 MHz, DMSO-d₆): δ 3.02 (t, 2H,

CH₂), 3.45 (t, 1H, OH), 3.70 (t, 2H, CH₂), 6.99–8.75

(Ar-H), 7.04 (d, 2H, J=7.76 Hz, CH=CH), 10.27 (br. s,

6H, NH). Anal. Calcd for C₃₆H₃₀N₁₆Na₂O₁₆S₂: C, 41.07; H,

2.87; N, 21.29; S, 6.09. Found: C, 41.12; H, 2.90; N, 21.25; S,

6.12.

2,3-Dichloroaniline Derivative of OBA. (7g)

(7g) was prepared according to the general procedure using

2,3-dichloroaniline. Mol.Wt: 1010, Yield 82 %; UV-max/nm,

(de-ionized water) 460 nm; IR (KBr): 3366 (N-H), 1646

(C=C), 1599, 1406 (C=C, Ar), 1584 (C=N), 1487 (N-H),

1360 (-CH₃), 1302 (C-N), 1065 (S=O), 824 (S-O), 988

2,6-Diaminoanthracene-9,10-dione Derivative of OBA. (7k)

(7k) was prepared according to the general procedure using

2,6-diaminoanthracene-9,10-dione. Mol.Wt: 1163, Yield

J Fluoresc

87 %; UV-max/nm, (de-ionized water) 581 nm; IR (KBr):

3416 (N-H), 1656 (C=C), 1590, 1416 (C=C, Ar), 1567

(C=N), 1451 (N-H), 1398 (-CH₃), 1328 (C-N), 1050 (S=O),

Synthesis of OBAs (7a-I)

The triazine-stilbene fluorescent brighteners are widely used

in industrial application as whitening agents [11] and their

synthetic procedures are well known. Synthesis of optical

brighteners (7a-I) has been achieved by reacting 2,4,6-

trichloro-1,3,5-triazine (1) with twelve different novel organic

amines (2a-l). This reaction resulted in the formation of

dichlorotriazinyl intermediates (3a-l). The chemical structures

of the organic amines (2a-l) used are given in Table 1. These

include a variety of important organic amines viz., mono-, di-

and trisubstituted anilines, secondary amines, heterocyclic and

bi- and tricyclic amines. The Maintenance of a low tempera-

ture of 4–5 °C was found to be critical for the successful

coupling of triazine with aromatic amines. Condensation of

the dichlorotriazinyl intermediates (3a-l) with 4,4-

diaminostilbene-2,2′-disulfonic acid (4) afforded bis-

monochlorotriazine intermediates (5a-l) in good yields. Again

for conversion, the careful control of pH and temperature was

found to be important for the success of reaction. Finally the

nucleophilic substitution of (5a-l) with ethanolamine (6) was

achieved at 90–95 °C to furnish the new hybrid optical bright-

eners (7a-l). Deionized water was used throughout all of the

synthetic steps.

1

843 (S-O), 993 (=C-H, bend). HNMR (300 MHz, DMSO-

d₆): δ 3.03 (t, 2H, CH₂), 3.45 (t, 1H, OH), 3.74 (t, 2H, CH₂),

6.04 (s, 2H, NH₂), 7.04 (d, 2H, J=7.77 Hz, CH=CH), 6.75–

7.53 (Ar-H), 10.34 (br. s, 8H, NH). Anal. Calcd for

C₅₂H₄₀N₁₄Na₂O₁₂S₂: C, 53.70; H, 3.47; N, 16.86; S, 5.51.

Found: C, 53.66; H, 3.42; N, 16.88; S, 5.57.

Naphthalene-1,5-diamine Derivative of OBA. (7l)

(7l) was prepared according to the general procedure using

naphthalene-1,5-diamine. Mol.Wt: 1002, Yield 86 %; UV-

max/nm, (de-ionized water) 459 nm; IR (KBr): 3415 (N-H),

1643 (C=C), 1589, 1410 (C=C, Ar), 1582 (C=N), 1489 (N-

H), 1387 (CH₃), 1300 (C-N), 1088 (S=O), 824 (S-O), 986

(=C-H, bend). ¹HNMR (300 MHz, DMSO-d₆): δ 3.06 (t, 2H,

CH₂), 3.45 (t, 1H, OH), 3.78 (t, 2H, CH₂), 5.98 (s, 2H, NH₂),

6.67–7.42 (Ar-H), 7.05 (d, 2H, J=7.78 Hz, CH=CH), 10.40

(br. s, 8H, NH). Anal. Calcd for C₄₄H₄₀N₁₄Na₂O₈S₂: C,

52.69; H, 4.02; N, 19.55; S, 6.39. Found: C, 52.74; H, 4.05;

N, 19.49; S, 6.41.

The structures of the newly synthesized hybrid optical

brighteners (7a-l) were supported by FTIR, ¹HNMR and UV

spectral data. The FTIR spectra of all compounds revealed a

strong absorption in the range 3479–3366 cm^-1indicating the

presence of N-H group. The HNMR spectra of all com-

pounds showed broad singlet of N-H around 10.14 ppm and

Results and Discussion

A series of twelve new optical brighteners has been synthe-

sized by a three-step synthetic in good yields according to the

synthetic route depicted in Scheme 1.

1

Scheme 1 Three step synthetic

pathway to new stilbene-triazine

hybrid optical brighteners (7a-I)

J Fluoresc

Table 1 Structures of organic amines used in the synthesis of OBAs (7a-l)

Compd

amine

Compd

2g

amine

NH₂

Cl

2a

Cl

SO₃Na

H₂N

NO₂

NH₂

Cl

2b

2c

2d

2h

2i

N

H

SO₃H

H₂N

NH₂

Br

N

SO₃H

H

F

NH₂

NO₂

S

N

2j

NH₂

NO₂

O

NH₂

H₂N

2e

2f

2k

2l

NH₂

O

F

NH₂

Cl

NH₂

strong aromatic signals in the range of 6.15–8.75 ppm. In UV

spectra all compounds displayed characteristic absorptions in

the range 457–581 nm.

In the present research, synthesized optical brighteners are

derived from the heterocyclic moiety containing nitrogen

atoms. These synthesized OBAs (7a-I) show excellent stabil-

ity to light which is depicted from their light fastness values

which is 4–5 in majority of derivatives (Table 2). There are

bulky and polar substituents which prevent their trans to cis

geometry transformation. Fluorescence of prepared OBAs

(7a-I) is also high because of larger conjugation in derivatives

(Table 2).

Stereochemistry of OBAs

Nearly 80 % of all OBAs produced are derived from the

stilbene derivatives, which absorb in the ultra violet regions

at 340–50 nm and can subsist in the cis and the trans config-

urations. Optical brighteners in the trans form, can be made

both in the liquid and the solid forms, but their protection

against light is necessary as they change from trans isomer to

cis isomer which cannot penetrate into cotton fibers.

Effect of pH and Temperature on the Synthesis of OBAs

During the preparation of stilbene-triazine compounds a care-

ful control of pH was found be essential in order to avoid

J Fluoresc

Polyamide

Table 2 Light Fastness data of OBAs (7a-l)

Table 3 Hot pressing Fastness data of OBAs (7a–l)

Compd

Gray scale reading

Compd

Gray scale reading

Wool

Leather

Polyester

Polyamide

Wool

Leather

Polyester

7a

7b

7c

7d

7e

7f

4–5

3–4

4–5

4.5

4–5

3–4

4–5

4.5

4–5

3–4

4–5

4.0

4–5

3–4

4–5

4.5

7a

7b

7c

7d

7e

7f

4–5

3.0

3–4

3.5

3.0

4–5

4.0

5.0

4–5

4.0

3.0

4–5

3.0

3–4

3.5

3.0

4–5

4.0

5.0

4–5

4.0

4–5

3.0

3–4

3.5

3.0

4–5

4.0

4.5

4–5

4.0

3.0

4–5

3.0

3–4

4.0

3.0

4.0

5.0

4–5

4.0

3.0

7g

7h

7i

7g

7h

7i

3.5

3.0

3.5

5.0

4.5

5.0

7j

3.5

3.0

7j

7k

7l

3.0

7k

7l

3.0

formation of unwanted hydrolysis products which can reduce

the whiteness. The reactivity was decreased at each chlorine

replacement step in the triazine moiety by the introduction of

different nucleophiles which decrease the electropositive char-

acter of the triazine ring. The three chloro groups of 2,4,6-

trichlro-1,3,5-triazine moiety showed different reactivity de-

pending on the nucleophile used and the reaction temperature

[12]. It is a well known that the he first substitution takes place

around 0–5 °C, second at 30–45 °C and third at 80–90 °C.

This difference in reactivity enabled us to successively replace

the three chlorine atoms to accomplish the synthesis of OBAs

(7a-I) in good yields and high purity.

characteristic absorptions in the range 457–581 nm due to

main chromophoric groups NH and CH=CH but the com-

pound 7b showed hypsochromic shift (457 nm) due to the

presence of NO₂group and 7k showed bathochromic shift

because of NH₂groups which are electron donating and shift

wavelength to number (Fig. 1).

Blankophor BBU used commercially to give whiteness and

brightness to cellulosic fibers, having a light fastness 5 was

used as a standard. Wavelength of maximum absorption

(λ_max) of hybrid OBAs 7d, 7f, 7g and 7e is similar to that of

the standard, while the λ_maxof 7a, 7h and 7j has been shifted

very little toward the visible region. Compound 7k (λ_max

581 nm) showed marked deviation from the standard due to

the presence of more conjugated 2,6-diaminoanthracene-9,10-

dione moiety.

UV/Visible Absorption Study of OBAs

UV/ visible absorption was determined using freshly pre-

pared solutions containing 2×10⁻²g/L of the compounds in

deionized water and adjusting solution to pH 9 with NaOH aq,

using a 10 mm quartz cuvette. All compounds have

Table 4 Color Fastness to chlorine (ISO 105-EO3) and Whiteness data

of OBAs (7a-l)

Compd

Concentration (%)

Change of shade

Whiteness (CIE)

7a

7b

7c

7d

7e

7f

0.25

4–5

3–4

4–5

3–4

4–5

3–4

4–5

3–4

101.39

107.40

94.25

98.5

120

110

std

100

batch5

batch4

batch3

90

80

70

60

50

40

30

20

10

0

batch2

batch1

batch6

batch7

batch8

batch9

batch11

batch12

batch10

103.4

105.6

104.5

107.5

106.93

108.35

97.6

7g

7h

7i

7j

400

450

500

550

600

650

700

7k

7l

Wavelength (nm)

92.12

Fig. 1 Combined Reflectance Spectra of Synthesized OBAs

J Fluoresc

according to ISO-105-BO2 [13]. All the synthe-

sized OBAs (7a-l) preserved excellent light fast-

ness 4-5.

ii)

Color fastness to hot pressing:

This test was conducted to determine the resis-

tance of colors of textile fibers of all kinds and in all

forms to ironing and to processing on hot cylinders.

Tests are performed on dry as well as on wet textile

samples. The end use of the textiles usually deter-

mines which test should be performed. A dry spec-

imen or a dry specimen covered with a wet dry

cotton adjacent fabric or a wet specimen covered

with wet cotton adjacent fabric are pressed with a

heating device at a specified temperature for spec-

ified time interval. Test results for OBAs applied on

wool, leather, polyester and polyamide fibers are

given in Table 3.

Fig. 2 Graphical representation of whiteness of synthesized OBAs (7a-l)

Characterization of OBAs

Optical brighteners (7a-l) were applied at concentrations of

0.25 % relative to the weight of cotton fiber and were charac-

terized by various tests which fastness test (color fastness,

chlorine fastness, and wash fastness), physical tests, solubility

and stability tests, and softening agents effect test.

iii) Chlorine Fastness and Whiteness Index:

Chlorine fastness test was carried out according to

ISO-105-EO3 [14]. Whiteness Index (CIE) values

were obtained by using standard method [15]. The

whiteness was measured using Data Color Spectro-

photometer SF 600 with large area view, illuminant

D65, and 10^°observer. Each sample was measured

three times from different surface of fabric. The

average results are shown in Table 4, Fig. 2.

a) Fastness Properties

i)

Color Fastness of textile fibers to Light:

This method is used for determination of the

resistance of the color of textile fibers at all stages

of processing to the action of an artificial light

source. The side to be tested of the specimen of

fibers was exposed to light from xenon arc under

specified conditions and to a specified depth of

color, along with eight dyed wool standards. The

fastness was assessed by comparing the fading of

cloth with that of the standards. Results of light

fastness are shown in Table 2. Light Fastness was

measured using Xenon Arc Lamp method

b) Physical Characterization of OBAs

Physical characterizations of OBAs include the ap-

pearance, structure, pH, constitution, storage stability,

ionic character and wash fastness properties. Various

physical properties of synthesized OBAs are given in

Table 5.

c) Solubility and Solution Stability of OBAs

This test was performed to assess, up to what extent

Table 5 Physical Characterization of OBAs (7a-l)

Compd

Appearance

Chemical character

Ionic character

pH of 1 % Soln.

Storage stability

Wash fastness property

7a

7b

7c

7d

7e

7f

Light Yellow powder

Stilbene derivative

Anionic

8.5

8.0

7.5

8.5

7.25

8.0

7.5

8.5

8.0

8.5

7.5

Virtually unlimited

Good

7g

7h

7i

7j

7k

7l

J Fluoresc

NaClO

Table 6 Solubility and solution stability data of OBAs (7a-l)

Compd

Solubility (g/l) at 20 °C

Stability of solution

Hard water

Acid

Alkali

Na₂S₂O₄

H₂O₂

7a

7b

7c

7d

7e

7f

300

Very good

Not stable

7g

7h

7i

7j

7k

7l

OBAs are water soluble, because water is the universal

solvent which is most commonly used in textile and

leather industries. The solutions of OBAs are treated with

different reagents to study their effect on the properties

and applications of OBAs on different substrates. Solu-

bility and solution stability data of different synthesized

OBAs is given in Table 6.

softness. The weave also contributes to reducing or in-

creasing the fabric softness. Furthermore, a greater num-

ber of yarns per centimeter increase the stiffness of the

fabric, thus reducing its softness. Softness of fibers in-

cludes surface softness, surface smoothness and elasticity

(compression and stretching). Softening test was carried

out to determine the effect of different types of

softening agents, either OBAs precipitate out from

solution, lose their properties, or don’t penetrate into

fiber. All the synthesized OBAs (7a-l) showed ex-

cellent stability and compatibility toward various

softening agents except cationic softeners. The ef-

fects of different softening agents on synthesized

OBAs are summarized in Table 7.

d) Effect of Softening Agents on OBAs

As a general rule, each fiber has its specific softness

value, which depends on its chemical composition and

physical structure (less crystallinity = greater softness).

The fineness of the fiber or of the filament directly affects

the softness of the yarn (woolens, worsteds, microfibers

etc.). The yarn twist ratio is inversely proportional to its

Table 7 Solution Stability data

of OBAs (7a-l) toward different

Compd

Stability of solution

softening agents

Resin Pre condensates

Anionic & non-ionic

softeners

Anionic & non-ionic

wetting agents

Cationic softeners

7a

7b

7c

7d

7e

7f

Compatible

Not Compatible

7g

7h

7i

7j

7k

7l

J Fluoresc

4. Rüchel R, Behe M, Torp B, Laatsch H (2001) Usefulness of

optical brighteners in medical mycology. Rev Iberoam Micol

18:147–149

5. Hussain M, Khan KM, Ali SI, Parveen R, Shim WS (2009)

Symmetrically substituted 4,4′-bis-(1,3,5-triazinylamino)stilbene-2,

2- disulfonate derivatives as fluorescent brighteners. Open Text J 2:

53–58

6. Grabchev I (1995) The synthesis and properties of some triazine-

stilbene flourescent brighteners. Dyes Pigments 29(2):155–160

7. Martin PAW (2004) A stilbene optical brightener can enhance bac-

terial pathogenicity to gypsy moth (Lepidoptera: Lymantriidae) and

Colorado potato beetle (Coleoptera: Chrysomelidae). Biocontrol Sci

Tech 14:375–383

8. Seong IU, Joon KL, Yonghan K, Dae JB (2005) The synthesis and

properties of triazine-stilbene fluorescent brighteners containing the

phenolic antioxidant. Dyes Pigments 64:93–99

Conclusions

Twelve new stilbene-trazine hybrid optical brightening agents

were synthesized using industrially important organic amines.

The newly synthesized hybrid optical brighteners were ap-

plied to fabric on 0.25 % strengths and they exhibited high

whiteness values 92.12–108.35, close to commercially avail-

able optical brighteners. All of these optical brightening

agents exhausted completely in the bath and furnished good

whiteness and brightness effects on the fabric and paper.

Absorption maxima (λ_max) confirmed the presence of absorb-

ing chromophores. Due to their exceptional properties (light

fastness, wash fastness, rubbing fastness, stability to light in

solution and solid state, compatibility to softeners), these

optical brightening agents can potentially be employed for

their synthesis on industrial scale to replace the commercially

available optical brighteners.

9. O’Neal CL, Crouch DJ, Fatah AA (2000) Validation of twelve

chemical spot tests for the detection of drugs of abuse. Forensic Sci

Int 109(3):189–201

10. Dave G, Ana-Mabel M, William H, Trevor W (2000) Effects of

optical brighteners used in biopesticide formulations on the behavior

of pollinators. Biol Control 19:232–236

11. Alsins J, Bjorling M, Furo I, Egle V (1999) Dimer formation of a

stilbenesulphonic acid salt in aqueous solution. J Phys Org Chem 12:

171–175

12. Samaritani S, Peluso P, Malanga C, Menicagli R (2002) Selective

amination of cyanuric chloride in the presence of 18-crown-6. Eur J

Org Chem 9:1551–1555

References

1. Zhang H, Lei M, Du F, Li H, Wang J (2013) Using an optical

brightening agent to boost peroxide bleaching of a spruce

thermomechanical pulp. J Ind Eng Chem Res 52:13192–13197

2. Hagedorn C, Saluta M, Hassall A, Dickerson J (2005) Fluorometric

detection of optical brighteners as an indicator of human sources of

water pollution. Part I: Description and detection of optical brighteners.

http://www.ext.vt.edu/news/periodicals/cses/2005-11/part1.html

13. Textiles-Tests for colour fastness Colour fastness to artificial light:

Xenon arc fading lamp test (2008) 00105B02 08427 2008, MOD

ISO 105 B02:1994, GB/T 8427-2008

14. Colour fastness to artificial weathering (2005) Xenon arc fading

lamp test, 00497 19764 2005, ISO 497:1973 IDT, GB/T 19764-

2005

15. Tang Z, Li H, Zhao X, Zhou W (2013) A method to improve the color

stability of naturally green cotton AATCC58-63, AATCC Review

May/June 2013. http://www.aatcc.org

3. Radeva G, Valcheva E, Veleva S (2009) The role of the entropy factor on

the adsorption of an optical brightener on pulp. Turk J Chem 33:241–248

Article Doi

Novel stilbene-triazine symmetrical optical brighteners: Synthesis and applications

DOI: 10.1007/s10895-014-1392-1

Source and publish data:

Authors:

Article abstract of DOI:10.1007/s10895-014-1392-1

Full text of DOI:10.1007/s10895-014-1392-1

Products guided by the article

R&D Labs maybe for 2272-30-2

Relevant to this article

Hot Product