New achievements of Professor Song Jianxin's research group of Hunan Normal University: synthesis, structure and near infrared absorption of heterocyclic fused earring porphyrin

Because of their wonderful optical and electrical properties, lead porphyrins have attracted a lot of attention These compounds have potential applications in photodynamic therapy, two-photon absorption, nonlinear optics, organic conductive materials and photovoltaic materials In the past, a variety of aromatic ring fused mononuclear porphyrins have been synthesized The π electronic system of porphyrins in these compounds has been expanded Therefore, the maximum absorption wavelength of porphyrins in the UV-vis-NIR region has red shifted In some cases, the maximum absorption wavelength has even expanded to 1600 nm Although this kind of material has the property of near infrared absorption, its synthesis is difficult Recently, Professor Song Jianxin's research group of Hunan Normal University used the recently synthesized "earring porphyrin" as the skeleton, further modified it, expanded the π electron system in the system, and enhanced the interaction between the parent nucleus of the porphyrin and the earring, so that the final product has a good absorption in the near-infrared region Relevant research results were published in angew.chem Int ed (DOI: 10.1002 / anie 201903446) Brief introduction of Professor Song Jianxin's research group Professor Song Jianxin has been studying porphyrin chemistry since he joined Hunan Normal University in September 2011 Their interests are focused on the design, synthesis, properties and related supramolecular chemistry of porphyrins Many of these functional molecules have novel structure and some absorption in the near infrared region, so they have the potential to be used in photodynamic therapy Since 2014, the group has achieved the following results in this area （ J Am Chem Soc 2018 , 140 ,16553-16559; Angew Chem Int Ed 2017 , 56 , 12322-12326; Org Lett 2017 , 19 , 2654-2657; Chem.Commun 2017 , 53 , 11488-11491 ; Angew Chem Int Ed 2016 , 55 , 6438-6442; Chem Eur J 2016 , 22 , 8801-8804; Chem Eur J 2015 , 21 , 15328-15338; Angew Chem.Int Ed 2014 , 53 , 11088–11091 ）。 This indicates that Hunan Normal University has been at the international forefront in the design, synthesis and Performance Research of porphyrin functional molecules Prof song Jianxin, Professor of Hunan Normal University, doctoral supervisor, vice president of School of chemical engineering He graduated from the school of chemistry and chemical engineering of Hunan Normal University in 1996 and 1999 respectively In 1999, he was admitted to Hunan University for his doctoral degree In 2002, he visited the University of Florida in the United States In 2006, he was funded by the National Overseas Study fund and went to Kyoto University for postdoctoral research After that, he studied in Japan and returned to Hunan Normal University to teach in 2011 It has been supported by the National Natural Science Foundation of China, the research start-up fund for returned students of the Ministry of education, the innovation platform project of colleges and universities in Hunan Province, the discipline leader cultivation project of colleges and universities in Hunan Province, and the talent introduction project of Hunan Normal University Leading scientific research achievements: the synthesis and structure of heterocyclic fused earring porphyrin and its near-infrared absorption porphyrin and other aromatic ring fused molecules with large π conjugation system have potential applications in photodynamic therapy, two-photon absorption, nonlinear optics, organic conductive materials and photovoltaic materials Recently, the "earring porphyrin" developed by this group has been used as a framework for further derivatization, so that the π electron conjugation system in the system has been expanded, at the same time, the interaction between the parent nucleus of porphyrin and earrings has been enhanced, so that the new compounds formed have good absorption in the near red outer region In this paper, we use the single earring porphyrin 1 as the raw material, through simple and efficient low-temperature bromination reaction, we get the dibromo product 2 on the earrings Using the classical Suzuki coupling reaction, the thiophene group or BOC protected pyrrole group can be connected to the earrings to obtain the corresponding 3H or 7h (Fig 1) For 3h, 3pd can be formed by inserting metal, and then oxidized by FeCl3 to obtain the final product 4pd (Fig 2) For 7h, some deprotection - condensation reactions will take place in the process of its formation Compound 6h with one side n and compound 5h with two sides n will be obtained 5h, 6h and 7h can react with PD (OAC) 2 to obtain 5pd, 6PD and 7pd respectively If 7pd was separated and oxidized by FeCl 3, 8pd was obtained 8pd can be deprotected smoothly under the action of trifluoroacetic acid to form 9pd Fig 1 Synthesis of thiophene fused eardrop porphyrin (source: Angel W chem Int ed.) Fig 2 Synthesis of pyrrole fused eardrop porphyrin (source: Angel W chem Int ed.) from Fig 3, it can be found that compound 4pd has a distorted spatial conformation The Dipyrrole unit far away from earrings in porphyrin has obvious distortion compared with tripyrrole unit in earrings, and the torsion angle reaches 48.5 (2) ° which is significantly higher than the corresponding torsion angle in 1pd This suggests that the condensation of thiophene may have an effect on the conformation of the molecule Fig 3 Single crystal structure of 4pd (source: angel Chem Int ed.) 6PD is an asymmetric molecule and 5h is a symmetric molecule However, the difference between the two molecules is not significant, which shows that n-fused pyrrole ring is not well involved in the conjugation of the whole molecule The structural analysis of 8pd shows that the distortion degree of 8pd is higher than that of 4pd in two orthogonal directions However, the cavity in the center of earrings in 8pd is smaller than that in 4pd, which shows that compared with 2,3-pyrrole condensation, 2,3-thiophene condensation has more influence on the skeleton of earrings porphyrin Fig 4 Single crystal structure of a, b) 5h; C, d) 6PD; E, f) 8pd (source: angelw Chem Int ed.) the author has studied the UV-vis-NIR spectra of the above compounds The UV-vis-NIR spectra of 1pd, 4pd, 5pd and 9pd are shown in Fig 5 It was found that the spectra of 3pd of simple thiophene coupling compound were similar to those of 1pd of raw material, but the spectra of 4pd and 9pd were significantly different from those of the former two The Soret bands in 4pd and 9pd spectra split, while the Q band shifted significantly, and the maximum absorption wavelength reached 2200 nm This shows that the π conjugation system in the two molecules has been expanded, and that the earrings have anti aromaticity As far as the authors know, the maximum absorption wavelengths in the UV-vis-NIR spectra of 4pd and 9pd are the largest among the known mono porphyrins Figure 5 1pd, 4pd, 5pd, The calculated chemical study of 9Pd (source: Angew Chem Int Ed.) shows that the maximum absorption wavelength corresponds to the orbital transition of the molecule HOMO-LUMO, which includes the charge transfer process from porphyrin to eardrop, indicating that the conjugation between the D orbit and π orbit of Pd also contributes to this The results of cyclic voltammetry and differential pulse voltammetry show that the first oxidation potential and the first reduction potential of 4 PD and 8 PD are lower than those of 3 PD and 7 PD The HOMO-LUMO energy level calculated by electrochemical method is in good agreement with the corresponding UV-vis-NIR spectrum The unique structure of these compounds makes them have potential applications in photodynamic therapy, two-photon absorption, nonlinear optics, organic conductive materials and photovoltaic materials The experimental part of the thesis is mainly completed by Wu Licheng, Li Feilong, master's student and Rao Yutao, doctoral student Review of previous reports: research group of Professor Song Jianxin of Hunan Normal University: synthesis and structural characterization of a new ring expanding porphyrin smaragdyrin Today, science and technology elements are increasingly valued in economic life, China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information, chembeangoapp, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.