Study On The Diradical Dications Of Nitrogen-containing And Antimony Monoradicals In The Fifteenth Group

Radicals are a class of atoms,molecules and ions containing unpaired electrons.Since the discovery of Moses Gomberg in 1900,the generation,structure,chemical reaction properties of radicals have attracted much attention.Radical chemistry is closely related to reaction mechanism,structural chemistry,materials chemistry,physical chemistry and biomedical fields.Because radicals containing unpaired electrons are usually very active,the lifetime of most radicals are very short.If there are no stabilization factors exist,they will quickly occur dimerization or disproportionation,and they can also react with hydrogen abstraction or oxygen addition.In this paper,a series of nitrogen-containing diradical dications,triarylstibine or triarylarsenic radicals were synthesized by using steric hindrance substituents and weakly coordinating anions.The structures and properties of the obtained radicals were studied in details which provided a reference for construction of the fifteenth group elements-based of new magnetic functional materials.This paper mainly includes the following four aspects:1.tetrakis(4-methoxyphenylphenylamino)-2,3,5,6-tetramethylbenzene diradical dication 12+ were successfully prepared by using weakly coordinated anion.The structure and chemical properties were studied by experiments and theorietical methods.Over the temperature range of 118-131 K,the magnetic measurements showded a 13 K hysteresis loop,leading to magnetic bistable.The coupling strength in the low temperature state is twice that of the high temperature state.Crystal structure analysis,EPR simulation,SQUID measurements,theoretical calculations show that the magnetic bistability is mainly due to the intramolecular electronic coupling.The study shows that it is possible to obtain a series of organic magnetic molecules similar to transition metal complexes through intramolecular electron coupling,which could play an important role in the field of organic free radical chemistry and bistable magnetic materials.2.A series of 1,2-di(bisarylamino)benzenes were synthesized and the corresponding dications were successfully isolated.The geometrical structures and electronic structure properties were studied by various experimental methods and DFT calculations.The ground state of 62+ and 72+ show a strong dependence on the bridge.The ground state of 62+ is an open-shell singlet diradicaloid in the solid state,and it is easy to excite into a triplet state at elevated temperatures.The ground state of 72+ is a triplet state.Such a tuning was achieved by increasing the steric hindrance of the benzene rings.Our work provides an example of nitrogen-containing analogues of stable m-benzoquinone with strong diradical properties,and the state of ground state of the compounds could be controlled by a bridged benzene rings,which laid a solid foundation for the developments of functional materials.3.A series of 1,3-di(bisphenylamino)benzenes were synthesized and the corresponding dications were successfully isolated.The geometrical structures and electronic structural properties were studied by various experimental methods and DFT calculations.For 82+-102+,both show quite significant diradical properties and the small singlet-triplet energy gaps.82+ shows stronger diradical character,and unexpectedly displays non-Kekule resonance structure.82+ unexpectedly displays non-Kekule character with a very trival contribution weight of the Kekule resonance structure.Syntheses of more species of such non-Kekuld type diradical dications with dififerernt substitutents and bridges as well as their reactivity studies are in progress.4.A series of diradicaloid dication with Wurster's blue(TMPD)were successfully stabilized and isolated as spin-carrying units by using of weakly coordinating anions.The geometries and electronic structures were studied by various experimental methods in conjunction with DFT calculations.Either using a saturated bridges or unsaturated bridges,both diradicals show considerable diradical character and the small singlet-triplet energy gap.112+,122+ and 132+ diradicaloid dication show significant diradical character with spacer-dependent singlet-triplet energy gap based on SQUID measurements.It is worth noting that 122+ exhibits much more enhanced diradical character and could basically regarded as a pure diradicals with degeneracy of the singlet and triplet states.We also explored the properties when two TMPD units were connected by benzene ring and aza-18-crown-6(142+ and 152+).The ground state of 142+-152+ is open shell singlet and is easily thermally excited to triplet.This work indicates that synthesis and stabilization of high-spin oligomers and polymers by catenation of Wurster's blue radical dications through methyl groups might be possible.Applications of these newly synthesized diradicaloid dicationic systems to electro-optical materials and further work to extend them to polymeric systems are under way.5.It was found that the use of AgSbF6 and Na[BArylF4]could oxidize the triarylstibine compounds containing large sterically hindered aryl ligands to obtain stable corresponding cation radicals,16+[BArylF4]-?17·+[BAryIF4]-.The radicals were characterized by single-crystal X-ray diffraction,nuclear magnetic resonance,electron paramagnetic resonance and ultraviolet-visible absorption spectroscopy,and their electronic structures were studied by theoretical calculations.According to paramagnetic resonance spectra and theoretical calculations,it is found that the spin centers of the radicals are mainly distributed on antimony.We also investigated the reactivity of free radical 17+[BArylF4]-,where 17+[BArylF4]-reacted with p-benzenedione,nBu3SnH,TEMPO to give compounds 182+[BArylF4]2-,19+[BArylF4]-and 20+[BArylF4]-.These reactive studies further confirm that the spin density are mainly resides on the antimony atoms.This work not only speeds up the radical chemistry of nitrogen radicals,but also provides a method to synthesize other stable main group metal radicals.