Synthesis, vibrational spectroscopy and X-ray structural characterization of novel NIR emitter squaramides.

Two new 2-naphthyl squaramides, 3-methoxy -4-(2-naphtalenylamino)-3-cyclobutene-1,2-dione (SQ-NPh1) and bis-3,4-(2-naphtalenylamino)-3-cyclobutene-1,2-dione (SQ-NPh2) were synthesized via condensation reaction between the dimethylsquarate and 2-naphthylamine. The spectrometric characterization by 13C NMR confirmed the obtaining of the squaramide derivative and nor the squaraine analog. This hypothesis was corroborated by Raman and Infrared spectroscopy since the characteristic vibrational bands related to the oxocarbon portion of both structures have been assigned, such as the ones for SQ-NPh1 and SQ-NPh2. The single-crystal X-ray crystallography for SQ-NPh1 crystal structures have been solved and the structure of SQ-NPh2 have been refined using Powder Diffraction state-of-art. The SQ-NPh1 crystallizes in monoclinic system in P2/c space group. Both squaramides present absorption in the ultra-visible (220-370 nm) and fluorescent emission in the near-infrared (780-800 nm), besides they also presented high thermal stability (around 570 °C). Generally, only squaraines are reported as NIR emitters, this is the first description of NIR emission for squaramides, and since the synthesis of squaramides is very easy and the rational design of small-molecule NIR fluorophores is of high priority and great value, these results are very promising for the development of novel NIR fluorescent dyes.

Raman spectroscopy and electronic microscopy structural studies of Caucasian and Afro human hair.

Human hair fibre is subjected to various structural modifications due to the application of chemicals such as dyes, shampoos and bleaches and/or physical procedures such as heating, and often more than one procedure is performed on the same hair. The present work aims to analyze the changes incurred in hair samples of two ethnic groups, namely Caucasian and Afro, before and after different treatments such as thermal, bleaching and straightening. In addition to observing the damage caused by each treatment separately, the study of samples that received all three treatments was carried out. For molecular structural characterization, the Raman vibrational spectroscopic technique was used and scanning electron microscopy (SEM) was used for morphological analysis of the hair fibres. This investigation has shown, through vibrational spectroscopy, that several important bonds have been modified, such as the S-S, C-S, C-C and S-O bonds as well as the secondary structures of proteins that have indergone changes in their conformation as a result of the treatment. Hair from the two ethnic groups showed small differences in relation to each applied treatment. Excessive heat generated a higher rate of Raman spectral band intensity changes when compared to the other treatments and it was observed that the action of several treatments on the same hair fibres resulted in even more pronounced structural changes. Finally, scanning electron microscopy showed that each treatment caused a different morphological deformation pattern on the capillary surface of the human hair.