Universal Set of Dyes for Digital Inkjet Textile Printing

NTC Project C03-PH01 

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Universal Set of Dyes for Digital Inkjet Textile Printing 

Project Leader: 

Hitoshi Ujiie, Philadelphia University, Philadelphia, PA 19144 

Participating Principle Investigators: 

Dr. Krishna Bhat, Philadelphia University 

Dr. Charles Bock, Philadelphia University 

Dr. Nancy Jo Howard, Philadelphia University 

URL address: http://faculty.philau.edu/ujiieh 

Project Goal: 

The goal of this project was the creation of an integrated, professional team of scientists within 

the Center for Excellence of Digital Inkjet Printing for Textiles at Philadelphia University 

devoted to the development of a universal set of dyes suitable for digital inkjet (DIJ) printing on 

diverse textile substrates. The Center is dedicated to fundamental research aimed at improving 

the performance and environmental compatibility of chemicals used for DIJ printing in the US 

textile industry. 

Abstract: 

The research team designed dyes with chemoselective affinity for DIJ printing applications, e.g. 

the boronic acid functional group was grafted onto the anthraquinone chromophore to act as a 

diol-recognition moiety for selected polysaccharides. Molecular modeling was used to establish 

potential dye/fiber affinity of cellulosic materials; chemoinformatics was used to establish 

quantitative structure activity relationships (QSARs) for colorant mutagenicity. 

Background: 

The textile industry in the United States is changing rapidly and it is evident that there is a need 

for a textile printing system that has the capacity to keep pace with current, as well as future, 

mass customization manufacturing requirements. DIJ printing has the potential to provide such 

capacity but, due to its relatively slow application speed at present, this printing process has not 

been generally adopted for full-scale production. 

Engineering improvements in DIJ hardware are expected to increase application speeds in the 

future, but there are also problems with various chemistries required by these systems, and these 

issues must be addressed if this technology is to reach its full potential. For example, companies 

that process substrates with different chemical character face expensive and time consuming 

operations whenever ink/fabric combinations must be changed. Indeed, many firms are forced to 

utilize a single printer for each ink/fabric combination to prevent frequent ink cartridge changes, 

an expensive operation. The availability of a set of dyes for DIJ printing that could function on 

multiple textile substrates would benefit the textile industry by decreasing the need for 

companies to maintain a complex inventory of colorants, reducing machine down time, and 

minimizing the amount of dyes contained in printing effluents. 

National Textile Center Annual Report: November 2006

Approach: 


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A multi-disciplinary approach was used in this project: the team consisted of an organic chemist, 

textile chemist, computational chemist and a DIJ specialist. Developing dyes that exhibited 

chemoselective affinity for specific textile substrates was a formidable task because of the 

hydrophobic nature of some substrates (e.g. polyester, nylon) and the polar or ionic nature of 

others (e.g. cotton, silk). The core idea in this project was to incorporate chemical-sensor 

subgroups onto chromophores that would serve as affinity ligands and effectively distinguish 

between different substrate functional groups. This type of approach has proved to be beneficial 

in medicinal chemistry [1], but has not been explored in the context of textile chemistry. 

A practical synthetic methodology was developed in the first year of this project that 

incorporated azo-functionality onto an anthraquinone chromophore to provide extended 

conjugation (Schemes 1, 2 and Figure 1). 

Scheme 1. Synthesis of anthraquinone dyes containing azo linkages synthesized from 1- 

aminoanthraquinone. 

Scheme 2. Synthesis of an anthraquinone dye containing boronic acid functionality. 



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Figure 1. Structures of Selected Anthraquinone Dyes from Molecular Modeling. 

This chemistry in Scheme I and 2, which is amenable to automation, was demonstrated in the 

synthesis of several compounds containing this novel azo-anthraquinone skeleton. All the new 

compounds generated via this synthetic route were thoroughly characterized by physical data, 

see Table 1. Technical textile properties, e.g. lightfastness, washfastness, and substantivity, were 

assessed by conventional procedures, see Table 2. 

Compound 

Yield 

(%) 

Melting 

Point (˚C) 

λ max 

(nm) 

UV (Methanol) 

Log ε 

2 65 228-229 475 3.45 

3 80 239-240 430 3.84 

4 78 242-243 410 3.18 

5 65 237-238 472 3.18 

6 70 230-231 470 3.43 

NMR (δ) 

3.5(2H, s), 6.5-6.7(4H, m), 7.3- 

8.1(7H, m) 

3.1(6H, s), 6.6-6.8(4H, m), 7.4- 

8.1(7H, m) 

5.8(1H, s), 6.9-7.1(4H, m), 7.4- 

8.2(7H, m) 

3.8(3H, s), 6.8-7.2(4H, m), 7.4- 

8.2(7H, m) 

7.2-7.5(4H, m), 7.6-7.7(2H, m), 7.8- 

8.2(7H, m) 

Elemental Analysis 

Found (Calculated) 

C H N B 

73.30 

(73.38) 

74.27 

(74.35) 

73.61 

(73.67) 

73.12 

(73.16) 

67.50 

(67.45) 

4.01 

(4.06) 

4.77 

(4.82) 

4.05 

(4.12) 

3.63 

(3.68) 

3.70 

(3.68) 

12.78 

(12.84) 

11.05 

(11.82) 

8.11 

(8.18) 

8.48 

(8.53) 

7.90 

(7.87) 

3.00 

(3.04) 

Table 1. Physical Data for Compounds in Scheme 1. 

Washfastness* 

Lightfastness** (20 hr & 40 hr exposure) 

Dye 

Polyester Nylon Cotton Silk 

Polyester Nylon Cotton Silk 

20hr 40hr 20hr 40hr 20hr 40hr 20hr 40hr 

2 5 4 1 2 5 3-4 3 2-3 5 5 3 2-3 

3 5 5 1 2 4-5 3-4 3-4 3-4 5 4-5 3 2 

4 5 5 1 1-2 4 3 2-3 3 5 5 3-4 3 

5 5 5 1 2 4-5 3-4 3-4 2 5 5 3 2-3 

*Washfastness AATCC Test Method 61-1996 (Test No.2A) 

**Lightfastness AATCC Test Method 16-1998 

Table 2. Washfastness and Lightfastness of Dyes 2 – 5. 



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One thrust of this project in the first year was to determine the extent to which boronic acid 

functionality introduced into anthraquinone and/or azo dyes, enabled the binding of the resultant 

dye to cellulosic textile materials; computational chemistry was employed for this purpose. 

Boronic acids are known to form borate complexes with saccharides containing diol moieties 

with a high degree of cis/trans specificity [2,3]. Calculations at the B3LYP/6-311++G** and 

MP2/6311++G** levels were carried out to establish the thermodynamics and kinetics of the 

formation of a typical boron-oxygen-carbon (B-O-C) bond. 

In the first year, the formation of a B-O-C linkage was studied using the dehydration reaction, 

H 2 B(OH) + H 3 C-OH H 2 B-O-CH 3 + H 2 O, 

as a model. It was shown that the process was initiated by a nucleophilic attack of the hydroxyl 

oxygen on the electron deficient boron atom of the reactant H 2 B(OH). This reaction was 

predicted to proceed rather slowly. However, a proton transfer was involved in this process, and 

it was established that an external Lewis base, such as ammonia, improved the kinetics of the 

reaction [4]. 

In the second year our experimental efforts were expanded to incorporate two binding sites on 

the dyes being synthesized. In addition to the boronic acid moiety, we initially incorporated a 

reactive guanidinium moiety on the dye framework. The cationic nature of the guanidinium 

group was expected to enhance both the solubility properties of the dyes and improve 

electrostatic interactions with ionic substrates. The power of including a guanidinium group for 

the binding of anionic guest molecules in competitive media has been demonstrated [5]. 

Synthesizing such dyes with two reactive groups proved to be quite challenging, but we 

eventually developed a methodology to incorporate the guanidinium group onto an anthracene 

unit in a single step, using a modified version of the Mitsunobu reaction, Scheme 3 [6]. Since 

the use of solid supports to facilitate combinatorial synthesis has become a popular way of 

generating libraries of new compounds with desired properties, we also extended our procedure 

to include the use of polymer supported reagents as a means of facilitating purification. 

DEAD, Ph 3 P in Toluene 

N,N' di Boc-guanidine 

H 2C 

OH 

H 2C 

N 

C 

NH 2 

Boc 

N 

Boc 

Scheme 3. Synthesis of a guanidinium moiety using the Mitsunobu reaction. 

In the second year calculations were performed on a system in which an internal Lewis base 

could expedite the formation of a B-O-C linkage. Specifically, we investigated the 

thermodynamics and the kinetics of the reaction, 

H 2 N-CH 2 -CH=CH-B(OH) 2 + H 3 C-OH H 2 N-CH 2 -CH=CH-B(OCH 3 )(OH) + H 2 O, 

in which the amino group acted as an internal Lewis base. We showed that when this amino 

group was appropriately positioned, it lowered the activation barrier for the formation of product 



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[7]. These results guided us to develop synthetic techniques designed to graft a variety of Lewis 

bases onto our molecular framework in the vicinity of the boronic acid moiety. 

Calculations in the second year of the project were performed on the second step in the boronic 

acid-diol complexation reaction; ethylene glycol was used in place of methanol resulting in the 

formation of a second B-O-C linkage. A 5-membered cyclic ester, HB(-O-CH 2 -CH 2 -O-), was 

generated via the reaction, 

HB(OH) 2 + HOCH 2 -CH 2 OH HB(-O-CH 2 -CH 2 -O-) + 2H 2 O. 

In the absence of any catalysts, the activation barriers for both steps involved in this reaction 

were rather high and the reaction was predicted to proceed rather slowly. 

The need to develop dyes with minimal adverse genotoxic behavior was also addressed 

computationally during the second year using semi-empirical quantum chemical methodology. 

Quantitative structure–activity relationships (QSARs) were developed for the mutagenicity of a 

variety of azo dyes. This has been accomplished within the context of the largest database of 

amino compounds for which the mutagenicity has been measured that has ever been assembled – 

over 180 amino derivatives are currently in the database. Multilinear regression techniques were 

shown to account for approximately 66% of the observed mutagenic behavior of the compounds 

and artificial neural network (ANN) approaches, in conjunction with fuzzy logic, [8] accounted 

for more than 90% of the variation. These QSARs provide a preliminary screening device for 

new dyes. 

During the third year of this project synthetic difficulties required us to look for alternatives to 

the inclusion of the guanidinium moiety. In particular, we considered non-aromatic nitrogenous 

structures with the capacity to form the intramolecular 5-membered ring, 7-membered ring, or 

Zwitterions when proximal to a boronic acid moiety shown below. 

H 2 

C 

N 

CH 3 

R 

B 

O 

B 

HO 

HO 

OH 

5-membered ring 7-membered ring HO 

Zwitterion 

H 2 

C 

CH 3 

R H 2 

N 

C 

H 

B 

OH 

NH 

OH 

R 

CH 3 

Our initial synthetic efforts focused on synthesizing binding sites at the 9,10 positions of the 

anthracene chromophore that would facilitate Lewis acid-base intramolecular interaction 

between nitrogen and boron. The first route utilized a two-step reduction [9] of the di-functional 

aldehyde, 9,10 anthracene dicarboxaldehyde, followed by reaction of the resultant imine with a 

primary amine, α-methylbenzylamine, using sodium borohrydride (NaBH 4 ) to produce a reactive 

iminium ion. The subsequent reaction with 2,4,6-tris[o-(bromomethyl) phenyl]boroxine 

(“boroxin”) produced the di-functional boronic acid moieties. Isolation, purification, and 

characterization of the intermediates and product proved to be very difficult. 

A one-step synthesis of similar compounds was explored using the cyanohydridoborate anion 

(BH 3 CN - ), which selectively reduced aldehyde and imine functional groups, Scheme 4 [10]. 

Careful adjustment of pH and temperature provided a means of controlling undesirable, 

competing side reactions. The di-functional aldehyde, 9,10 anthracene dicarboxaldehyde, and a 



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mono-functional aldehyde, 9-anthraldehyde, in combination with methylamine, were reacted 

under similar conditions. Although the one-pot process was attractive for use in combinatorial 

syntheses, excessive reaction time [72-96 hours], and production of toxic hydrogen cyanide gas 

as a by-product, made this synthetic route undesirable. 

H 3C 

N 

O 

H 

H 

HN 

CH 3 

H 

NaBH 3 CN 

CH 2 

CH 3 

CH 2 

boroxin 

CH3CN 

K 2 CO 3 

Reflux 

B(OH) 2 

C 

H 2 

N 

Scheme 4. One-step reductive amination using the cyanoborohydride followed by a reaction 

with boronic acid anhydride. 

A one-step reductive amination reaction conducted using triacetoxyborohydride provided a safer 

alternative, Scheme 5 [11]. The reducing agent converted stoichiometric amounts of the 

dicarboxaldehyde and 1 º amine (methyl amine or α-methylbenzylamine) to the corresponding 2 º 

amines in high yields, requiring a much shorter reaction time [20 min.- 2 hr.], while producing 

only small amounts of benign by-products. Due to the high reactivity of the free amines, an 

oxygen-free environment was required throughout the reduction reaction. Stable ammonium 

chloride salts were isolated, and purification and characterization are currently being carried out. 

It was anticipated that, by maintaining an oxygen-free environment, the reaction with 2,4,6- 

tris[o-(bromomethyl)phenyl] boroxine can be conducted immediately following the reductive 

amination without the HCl salt formation. 

CH 3 

H 3C 

Ph 

Ph 

CH 

N 

H 

O 

H 

H 

CH 

HN 

CH 2 

H 3C 

Ph 

CH 

N 

H 2 

C 

(HO) 2B 

H 

HB(OAc) 3 Na 

DCE 

H 2C 

boroxin 

CH3CN 

K 2 CO 3 

Reflux 

CH 2 

B(OH) 2 

C 

H 2 

H 2C 

N 

Ph 

CH 

CH 3 

H 

H 

O 

N 

Ph 

Amine 

NH 

CH 

CH 3 

Ph CH 3 

Scheme 5. One-step reductive amination using the triacetoxyborohydride followed by a reaction 

with boronic acid anhydride. 

Computationally in the third year we focused on studies designed to elucidate the 

thermochemistry of the reaction between phenylboronic acid (PBA) and a sinple model 

cellulosic substrate. The initial model of cellulose chosen for this study, C 1 , was a singlestranded 

molecule composed of four repeating anhydroglucose units. The structure of this 

molecule was optimized using density functional theory (DFT) at the LDA/6-31G* (B3LYP/6- 

31G*) computational levels with the Spartan software package from Wavefunction Inc. [12], see 

Figure 2. The initial geometry for the optimization was chosen to incorporate the expected 

intramolecular hydrogen bonding [13], whereas intermolecular hydrogen bonding between 

different strands in cellulose was completely ignored in these investigations. 



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Figure 2: Model Cellulosic Substrate. 

Two models for the product of a dehydration reaction of this cellulose molecule and PBA were 

investigated. This dehydration is the primary reaction required to bind a dye, designed with 

boronic acid functionality, to a cellulosic substrate. The first model product, P 1 , employed the 

2,6’-hydroxyl groups of the model substrate, see Figure 3; it involves hydroxyl groups on two 

different adjacent glucose units. The second model, P 2 , employed two hydroxyl groups on the 

same glucose unit that are in a 2,3 cis arrangement, see Figure 4. 

Figure 3: Hydration product, P 1 , involving the 2,6’-hydroxyl groups. 

Figure 4: Hydration product, P 2 , involving the 2,3-hydroxyl groups (cis). 

Interestingly, the structure of P 1 is 8.4 kcal/mol lower in energy than P 2 at the LDA/6-31G* 

computational level, whereas these two rather different structures have nearly the same energy at 

the higher-level B3LYP/6-31G* computational level, see Table 3. 



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Reaction 

ΔE(kcal/mol) 

C 1 + PBA → P 1 +2H 2 O +23.4 (21.5) 

C 1 + PBA → P 2 +2H 2 O +31.8 (20.1) 

Table 3: Dehydration reaction energetics for a model boronic acid dye-cellulose complex. 

For comparison, calculated reaction thermodynamics for the formation of a single B-O-C linkage 

in the dehydration reaction: 

H 2 N-CH 2 -CH=CH-B(OH)H + H 3 C-OH → H 2 N-CH 2 -CH=CH-B(OCH 3 )H + H 2 O 

are essentially thermoneutral: ΔH o 298 = -0.2 kcal/mol at the MP2(FULL)/6-311++G** 

//B3LYP/6-311++G** level [7]. 

Acknowledgements 

The PI wishes to thank graduate students Pavani Nandula, Ravneet, Amadeep Randhawa and the 

undergraduate student Heather Vodzak. 

References: 

1. Yang, W., Gao, X., Wang, B., Med. Res. Reviews (2003) 23, 346. 

2. Springsteen, G. and B.Wang, Tetrahedron (2002) 58, 5291. 

3. Pawlowski, N. E., D.D. Russell and K.M. Robotti, USP 5,108,502 (April 28, 1992). 

4. Bhat, K.L., Hayik, S. & Bock, C.W., J. Mol. Struct (Theochem) (2003) 638, 107. 

5. Best, M.D., S.L. Tobey and E.V. Anslyn, Coordination Chemistry (2003) 240, 3. 

6. Yang, Y., B. Wang, Chem Comm (2003) 792. 

7. Bhat, K.L., Braz, V., Laverty, E. & Bock, C.W., J. Mol. Struct (Theochem) (2004) 712, 9. 

8. Bhat, K.L., S. Hayik, L. Sztandera & C.W. Bock, Chem Info & Comp Sci (2004) submitted. 

9. Ward, C.J., P. Patel, P.R. Ashton and T. James, Chem Commun (2000) 229-230. 

10. Borch R.F., M.D. Bernstein and H.D. Durst, JACS (July 16, 1971) 93(12), 2897-2904. 

11. Abdel-Magid, A., K.G. Carson, B.D. Harris, C.A. Maryanoff and R.D. Shah, J. Org. Chem. 

(1996) 61, 3849-3862. 

12. Spartan ’02, Wavefunction, Inc., 18401 Von Karman Avenue, Suite 370, Irvine, CA 92612 

USA. 

13. Sturcova, A., I. His, T.J. Wess, G. Cameron, M.C. Jarvis, Biomacromolecules (2003) 4, 

1589.

Universal Set of Dyes for Digital Inkjet Textile Printing

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