Chemists synthesize the longest benzo decacene in history

Benzo (acene) is a kind of linear polycyclic aromatic hydrocarbons (PAHs) which is condensed in a small position Because of the special electronic properties of benzo, chemists are fascinated by it and have been exploring and studying it for decades The simplest parabenzenes are naphthalene and anthracene These two small molecules can be obtained by distillation from coal tar or heavy oil components However, the larger amount of p-benzene does not exist in natural resources, because the chemical stability of p-benzene in the environment decreases with the increase of the number of P-rings Because of their special π electron distribution, they have outstanding semiconductor properties For example, pentacene can be used as the material of field-effect transistor, and its hole mobility is higher than that of amorphous silicon Recent studies have also found that benzo has potential applications in the field of spin electrons It has poor solubility and high reactivity, especially the one without substituents It is very difficult to synthesize p-pentacene and above, which is called "terrible challenge" At present, the biggest benzo that can be separated in large quantities is heptacene, which took 75 years to complete until earlier this year There are two main synthesis methods of p-heptachyphenyl, one is obtained by photochemical reaction on polymer or inert gas matrix with bridge α - diketone as precursor, and the other method recently discovered is obtained by thermal cracking of p-heptachyphenyl on solid device Octacene and nonacene can also be produced by bridge α - diketone in inert gas at low temperature Fig 1 Source of heptachyphenyl: angelw Chem Int ed recently, a research team led by Dr Francesca Moresco from Dresden University of technology in Germany and Professor Diego PE ñ a from the University of de Compostela in Santiago, Spain, synthesized the longest benzo decacene ever, and used scanning tunneling microscope (STM) The structure of p-decarbene was observed by STM Figure 2 Source of synthesis strategy of p-decarbene: the development of angew Chem Int ed surface chemistry has opened up a powerful alternative way for chemists to obtain highly active molecules from stable and soluble precursors For example, triangulene can be formed on the surface at low temperature and ultra-high vacuum, and characterized by scanning tunneling microscopy and atomic force microscopy (AFM) Previously, the research team successfully prepared tertacene through the surface chemical reaction of epoxy precursor on Cu (111) and hexacene through the deoxidization of triepohexabenzene on Au (111) Inspired by this, the team chose stable tetracycline derivative 5 as the reaction precursor and tried to generate p-decarbene on the surface of Au (111) The p-decacene precursor 5 can be obtained by three-step iterative cycloaddition of arylacetylene (see Fig 3) Figure 3 Source of iterative synthesis of p-decarbene precursor 5: in the process of surface formation of angelw Chem Int ed p-decarbene, precursor 5 was placed on a clean Au (111) surface at room temperature, and then sublimed under ultra-high vacuum STM and STS characterize the molecules separated on the surface at t = 5 K STM shows that p-decarbene has the same structure as a track Figure 4 STM characterization source of p-decarbene: angelw Chem Int ed p-decarbene is an achievement jointly created by synthetic chemists and surface scientists, which will solve more long-standing chemical problems Although p-decarbene is very unstable and can not be used in any practical applications at this stage, scientists still have great interest in its electronic properties and expect that it will play a role in the field of organic electronics like p-pentabenzene one day.