Modern Molecular Modeling Methods: Utility In Color Chemistry

Harold S. Freeman, Professor
Polymer and Color Chemistry Program
N.C. State University - College of Textiles

This ongoing program at NCSU was initiated in 1995, as part of a collaborative effort aimed at demonstrating the utility of molecular orbital (MO) theory as an approach to the design of state-of-the-art textile dyes, fibers, and chemical auxiliaries. A critical goal of this effort was to shorten the development time for new products, by reducing the number of compounds requiring synthesis and evaluation before a target agent is achieved. This goal was pursued, initially, by examining several commercially available molecular modeling software packages for their ability to produce data that correlated well with experimental results, especially X-ray and electronic spectral results. In this regard, PPP, MOPAC, and ZINDO were examined for their reliability in predicting the structure and technical properties of various polymers and synthetic dyes and pigments.

With regard to dyes and pigments, MO based modeling methods have been established that enable researchers to predict 1) molecular geometry, 2) color, 3) solubility properties, 4) light fastness, and 5) mutagenicity. For instance, we found that PiSystem, a PPP-based method, was preferred for predicting the color of a target dye or pigment, and that ZINDO, which was implemented using the CAChe Worksystem, was best for predicting molecular geometries. In turn, the resulting information has been used to explain why 1) iron-complexed azo dyes are inferior in color and technical properties to the corresponding iron-complexed formazan dyes, 2) diarylide pigments derived from twisted benzidines have low lightfastness, 3) certain isosteric replacements for ortho–OH groups fail to serve as ligands for metal complex formation in azo dye systems, and 4) multiple products are produced during oxido-reductase mediated dye synthesis.

Our work in this area has enjoyed financial support from the National Textile Center and Clariant Corporation. Papers published from our work include the following:

· J. Lye, D. Hinks, and H.S. Freeman, “Computational Chemistry Applied to Synthetic Dyes”, in Computational Chemistry and Chemical Engineering, G. Cisneros, J.A. Cogordan, M. Castro, and C. Wang, eds., World Scientific Publ., Singapore, 1997.

· J. Lye, H.S. Freeman, P. Singh, M.E. Mason, and D. Hinks, “Molecular Modeling Studies in Dye Chemistry: Part 1. Studies Involving Two Disperse Dyes”, Textile Res. J., 69(8), 583 (1999).

· Harold S. Freeman, Mary E. Mason, and Jason Lye, “Disperse Dyes Containing a Built-in Oxalanilide Stabilizer, Dyes and Pigments, 42, 53 (1999).

· J. Lye, H.S. Freeman, P. Singh, M.E. Mason, and D. Hinks, “Molecular Modeling Studies in Dye Chemistry: Part 1. Studies Involving Two Disperse Dyes”, Textile Res. J., 69(8), 583 (1999).

· Jason Lye, Harold S. Freeman, and Russell D. Cox, Molecular Modeling of Congo Red Analogs Containing Terphenyl and Quarterphenyl Moieties, Dyes and Pigments, 47(1-2), 53 (2000).

· K.L. Bhat, H.S. Freeman, J. Velga, L. Sztandera, M. Trachtman, and C.W. Bock, “Monomethoxy-4-aminoazobenzenes: a Computational Study”, Dyes and Pigments, 46(2), 109 (2000).

· El-Shafie, D. Hinks, H.S. Freeman, and J. Lye, “Semi-empirical Molecular Orbital Methods in the Design of Organic Colorants”, AATCC Review, 1(12), 23 (2001).

· J-S. Bae, H. S. Freeman, and A. El-Shafie, “Metallization of Non-genotoxic Direct Dyes”, Dyes and Pigments, 57(2), 121 (2003).

· Stephen D. Shaw and Harold S. Freeman, “Dyes from Enzyme-mediated Oxidation of Aromatic Amines”, Textile Res. J. 74(3), 215, 2004.

College of Textiles
P.O. Box 8301
Raleigh, NC 27695-8301
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Last Site Revision:
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