Li Dan, Professor of Jinan University: can achiral materials have optical activity?

It is generally believed that optical activity (optical activity and circular dichroism) is a special property of chiral materials However, are the non chiral substances necessarily not optically active? In fact, as early as 100 years ago, scientists Gibbs and Pockels predicted that non chiral substances crystallized in some point groups have optical activity More than 50 years later, relevant experimental reports have been published A review in 2008 (angelw Chem Int ed 2008, 47, 5706) mainly reported inorganic crystals and organic small molecular crystals with achiral point groups However, due to the lack of strong experimental evidence, this kind of unconventional phenomenon has not been widely recognized In 2016, a case of mononuclear zinc complex and copper complex crystallized in the achiral point group mm 2 was reported They show optical activity (NAT Mater 2016, 15, 591) Their circular dichroism (i.e ECD spectrum) signal is weak and only has a single direction Up to now, MOF with optical activity has not been reported Recently, Professor Li Dan's research group of Jinan University found a case of adenine based biomaterial organic framework material with non chiral structure but optical activity Relevant research results were published in J am Chem SOC (DOI: 10.1021 / JACS 8b06725) Prof Li Dan was awarded a bachelor's degree in chemistry from Sun Yat sen University in 1984 and a doctor's degree from Hong Kong University in 1993 From 1984 to 2016, he worked in Shantou University and served as vice president of Shantou University; from October 2016, he worked in Jinan University and now is the dean of the school of chemistry and materials of Jinan University Professor Li Dan is the winner of National Science Fund for Distinguished Young Scholars He has been engaged in the research of supramolecular coordination chemistry, and has successively presided over major research programs, key projects, general projects and national 973 Program (Project Leader), etc He has published more than 170 academic papers in international authoritative academic journals, such as J am Chem SOC., angelw Chem Int ed., chem Rev., with an H-index of 51, and cited more than 6000 SCI papers by him Professor Li Dan is the "government special allowance expert" of the State Council, selected as the leader of the "one million talents project" of the national ten thousand talents plan, the fourth batch of advanced individuals of the training objects of the "one hundred and ten projects" of Guangdong Province; he has won the first prize of science and technology of Guangdong Province (the first adult), and the "model worker" of Guangdong Province Li Jiacheng foundation of Shantou University, Guangdong Province Now he is FRSC, Council member of China Chemical Society, vice president of Guangdong chemical society and executive director of Guangdong material society Brief introduction of Professor Li Dan's research group in recent years, Professor Li Dan's research group has been devoted to the molecular design, synthesis and assembly, structural morphology, excited state physics and chemistry of coordination supramolecular assemblies, host guest chemistry in confined space and supramolecular chirality Frontier scientific research achievements: an example of non chiral structure of adenine based biomaterial organic framework material was found to have optical activity in the research process, Li Dan team found: an example of newly prepared adenine based biomaterial organic framework material (referred to as ZnFDCA, Fig 1) ）It is an achiral structure with symmetrical surface and no symmetrical center, but it has optical activity Znfdca is composed of the achiral components such as adenine, 2,5-furandioic acid and zinc nitrate The crystal is a two-dimensional layered structure, crystallized in the non chiral crystallography point group When the incident polarized light angle is different, the ECD signal with different intensity or even opposite direction may be obtained; when the incident light is just parallel to the main axis of the crystal, the ECD signal is not displayed Fig 1 structural diagram of znfdca (source: J am Chem SOC.) the researchers tested 20 randomly selected single crystals with KCl compression method one by one for solid-state ECD, and found that the achiral znfdca showed obvious optical activity In 20 sample measurements, 4 positive direction signals and 9 negative direction signals were recorded (Fig 2) The remaining 7 signals were not obvious Fig 2 solid state ECD test of single crystal (source: J am Chem SOC.) the author also designed a comparative experiment, adding an amino group to the biomolecule adenine ligand to obtain the topologically isomorphic metal organic framework znfdca-nh 2 Interestingly, znfdca-nh 2 does not exhibit optical activity due to its different symmetry In addition, based on their symmetry, the second-order nonlinear optical properties are also studied Chiral materials have optical activity, but not vice versa - under certain conditions, optical activity can also come from non chiral materials Many people have misunderstandings about this, and many textbooks do not write it, or even make mistakes This study provides a specific and powerful evidence, as the first case report of optical signals observed in an achiral MOF material, and strong positive and negative signals can be obtained This paper was selected as a cover paper by j.am.chem.soc (j.am.chem.soc 2018, 140, 11569) This achievement was completed by Jinan University in cooperation with Shantou University, Hanshan Normal University, Nottingham University (Malaysia) and Fujian Institute of material structure, Chinese Academy of Sciences Review of previous reports: Professor Li Dan of Jinan University / research team of Professor Zhou Xiaoping of Shantou University: self-assembly of chiral organopentagonal tetrahedron People and scientific research are increasingly valued in the economic life of scientific and technological elements Today, China has ushered in the "node of scientific and technological 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.