Near-infrared activated groups

The book is divided into seven chapters. Chapter 1 describes photo-chromic materials which have critical applications in memory technology. These compounds generally are activated by light. Chapter 2 covers leuco quinones which, in many cases, when oxidized, have their absorption maxima in the near-infrared region. Chapter 3 describes leuco dyes of a common group of compounds—oxazine, thiazine, and phenazines—that have found applications in color photography. Chapters 4-6 describe arylmethine-type compounds that can be triggered to dyes by common chemistry. Chapter 7 describes a special class of leuco dyes, namely, tetra-... 

As with the simple 1,4-naphthoquinones, most recent research activity in the heteroannelated compounds has been directed towards the development of dyes that absorb in the near-infrared. Noteworthy is the dithiadinaphtho-1,4-naphthoquinone system 16 (X = S), which can be prepared by condensing 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone with 2-aminothiophenol [25], The parent compound 16 (X = S) [96692-25-0] shows multiple absorption bands between 400 and 800 nm, with the most intense peak at 725 nm in chloroform (rmax 15 200 L mob1 cm-1) [25], Oxidation of the sulfur atoms to SO groups produces a large bathochromic shift, and 16 (X = SO) shows a peak at 827 nm (emax 17 600 L mol-1 cm-1) in chloroform [25],... 

Near-infrared absorption is therefore essentially due to combination and overtone modes of higher energy fundamentals, such as C-H, N-H, and O-H stretches, which appear as lower overtones and lower order combination modes. Since the NIR absorption of polyatomic molecules thus mainly reflects vibrational contributions from very few functional groups, NIR spectroscopy is less suitable for detailed qualitative analysis than IR, which shows all (active) fundamentals and the overtones and combination modes of low-energy vibrations. On the other hand, since the vibrational intensities of near-infrared bands are considerably lower than those of corresponding infrared bands, optical layers of reasonable size (millimeters, centimeters) may be transmitted in the NIR, even in the case of liquid samples, compared to the layers of pm size which are detected in the infrared. This has important consequences for the direct quantitative study of chemical reactions, chemical equilibria, and phase equilibria via NIR spectroscopy. 

A fiber optic probe was used by Blanco et al. for analysis of spasmoctyl samples with the active compound otilonium bromide and cellulose, maize starch, sodium starch glycolate, and glyceryl palmitostearate as excipients. Another study from this group covered the identification, qualification of the substance, and the quantification of the active component. A library search with a comparison to the near-infrared spectra of 163 pharmaceuticals was involved. An on-line monitoring for the determination of the endpoint of polymorph conversions in pharmaceutical processes was recently described further investigations into this field were published and are noted previously. ... 

Several of the polymethine dyes absorb in the red, far-red, and near-infrared and fluoresce efficienlly as well in this spectroscopic region. Functional derivatives of these may provide excellent fluorescent labels for semiconductor laser excitation. Several research groups are currently actively involved in the synthesis and development of large polyunsaturated dye molecules that are excited and show luminescence in the red and near-infrared. This promises to be one of the most exciting areas of luminescence spectroscopy for the foreseeable future. 

Maiman [4-6] has described the first laser systems (ruby) in the 1960s. The active medium in solid-state lasers is generally a transparent crystal or glass into which a small amount of transition metal is doped (e.g. Ti/sapphire, Nd YAG). There are two main types of semiconductor lasers those operating at fixed wavelengths and those which are tuneable. Diode lasers are the most prolific of all types of laser. Most of these lasers are semiconductor compounds of Group III and V species. Diode lasers operate mostly in the near-infrared but also in... 

One may well wonder why the in-phase cw-CH wag near 690 cm is so much lower in frequency than the in-phase trans-CYi wag near 970 cm" in the infrared spectrum. In Fig. 4.16, the lone CH wag of the C2C=CHC group has a frequency near 825 cm in hydrocarbons. It can be seen that this vibration twists the C C bond. Also in Fig. 4.16 are seen the in-phase and out-of-phase CH wag vibrations in trans- and cis-C—CH==CH—C groups. Only the in-phase wag is infrared active. In the trans isomer this in-phase vibration gives the C=C bond a double twist, and in the cis isomer the... 

Oxalate esters (—O—CO—CO—O—) have two carbonyl groups. These can vibrate in-phase, symmetrically, or out-of-phase, asymmetrically, to give rise to bands near 1765 and 1740 cm S respectively, for alkyl esters, and near 1795 and 1770 cm" respectively, for aryl esters. When the carbonyls are cis to each, other both in-phase and out-of-phase vibrations are infrared active, but when the carbonyls are trans to each other (as in the solid state) only the out-of-phase lower frequency vibration is infrared active. 

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