title: Structure-performance relationship for a family of disperse azo dyes having the same D-π-A 4-nitro-4'-amino-azobenzene skeleton: structures, solvatochromism and DFT computations.
abstract: A combinational study of structural chemistry and dyestuff chemistry has been carried out to reveal the structure-performance relationship for eight disperse azo dyes by comparing their structures, electronic spectra, solvatochromism and theoretic computations. All eight structural analogues have the same 4-nitro-4'-amino-azobenzene donor-π-acceptor skeleton but different substituted groups, namely, R1 and R2 in ring A, R3, R4 and R5 in Ring B. X-ray single-crystal diffraction analyses indicate that four azo dyes have severely twisted aminoazobenzene structures because of the steric hindrance of ortho dichloro/dibromo radicals of 4-nitrobenzene moiety, while the other four dyes show essentially planar conformation due to the ortho monosubstituted 4-nitrobenzene amine and 4'-amino-azobenzene units. It is noted that the electronic spectra are closely related to their molecular structures, where the presence of different auxochrome groups and the spatial crowding effects in the aminoazobenzene backbone lead to significant alterations of the bathochromic and hypsochromic shifts.
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu Province 210093, PR China.
authors.forename: Tao
authors.initials: T
authors.lastname: Tao
authors.affiliation: College of Sciences, Nanjing Tech University, Nanjing, Jiangsu Province 210009, PR China.
authors.forename: Yin-Ge
authors.initials: YG
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu Province 210093, PR China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu Province 210093, PR China; College of Sciences, Nanjing Tech University, Nanjing, Jiangsu Province 210009, PR China.
authors.forename: Hui-Fen
authors.initials: HF
authors.lastname: Qian
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu Province 210093, PR China. Electronic address: whuang@nju.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D012997:Solvents; C009850:azobenzene
keywords: Azo dye; Crystal structure; Electronic spectrum; Solvatochromism; Structure–performance relationship