Significant analytical reactions of elemental species are usually based on complex formation during which various types of complexes, chelates, ternary species, and ion association complexes of suitable stability and analytical properties may be formed. Organic complex-forming agents often give species which highly absorb radiation in the visible (VIS) and UV spectral range and have been under the scope of analysts for many years. The development and studies of organic analytical reagents have stimulated the progress and achievements in both analytical and coordination chemistry.