In 1907, Brown and others successfully synthesized the phthalocyanine compound for the first time; in 1927, German chemist DeDiesbach and others accidentally prepared copper phthalocyanine, but people did not know its structure at that time, until Lin-stead pointed out that Brown and Diesbach and others synthesized it in 1932. The substance is a phthalocyanine compound, and it is proposed to name all organic substances based on the compound H2Po as "phthalocyanine" to distinguish it from porphyrin. In the basic structure of phthalocyanine (6), R~R functional groups can be hydrogen atoms, alkyl groups, benzo groups, heterocycles, etc., and the nitrogen atoms in the central cavity can be combined with metal atoms such as N, Zn, Pt , Pd, A, Si, Ge, etc. The dye can also be used as a near-infrared stealth material.
The absorption spectrum of phthalocyanine dyes is similar to that of porphyrins and is divided into two main absorption bands: the B band in the ultraviolet region, the Soret band, and the Q band in the visible and near-infrared regions, but the strength of the absorption band is similar to that of porphyrin. On the contrary, the B-band of phthalocyanine is weak absorption and the Q-band is strong absorption. The Q band is affected by the number of fused benzene rings, substituents, etc. Amx is generally located in the near-infrared region of 650~850mm, which is 100-200mn redshift from the porphyrin Q band. The naphthalocyanine (7) formed by attaching benzo groups around the phthalocyanine is a very important kind of phthalocyanine compound. Due to the increase of the conjugated system, the corresponding red shift of the Q band will occur. The solution spectrum λmx is generally located at 750~850mm, which is about 100m red shifted from the corresponding phthalocyanine. The electron withdrawing group is introduced on the peripheral benzene ring of the phthalocyanine molecule. Clusters such as chlorine can also make the absorption band red-shift, while the absorption band of the metal atom is usually blue-shifted after the metal atom is introduced to the center of the phthalocyanine ring. This is mainly because the generation of the spectrum is caused by the transfer of electrons from the center of the molecule to the surrounding aromatic rings. When the metal atom is introduced into the center, its coordination effect will weaken the electron cloud density on the nitrogen atom. This point has been well proved from the theoretical calculation of the PPP MO method and the specific experimental results. Theoretically, the structure of the 18π electrons of the phthalocyanine molecule determines the range of the Amax redshift. According to the current literature, it is difficult to reach 900nm.
This type of dye has a wide range of applications in organic photoconductors, electrophotography, and laser printing systems, and has been reported as a photosensitizer in photodynamic therapy. This kind of dyes have good light-heat stability and chemical stability. They are a kind of coloring dyes with a long history, and some products are widely used. In terms of laser protection, phthalocyanine dyes started early in the United States. There were many related patents in the 1970s and 1980s. Most of their protection wavelengths are 650~750mm, which shows that this type of dye is in laser protection. It has certain application prospects. However, the preparation and purification methods of this kind of dyes are complicated, the absorption rate is generally low, the wavelength adjustable range is narrow, and most of the solubility properties are not good.