Study On Spin Multiplicity Manipulation And Optical And Magnetic Properties Of Naphthalimides

The spin multiplicity manipulation of excited state and ground state is very important in the fields of luminescence,magnetism and even quantum computing.In the field of luminescence,especially in organic room temperature phosphorescence,the key to the generation of organic room temperature phosphorescence is to promote the transformation from singlet state to triplet state.In the field of magnetism,orderly arrangement the spin is the major pain point for organic ferromagnetic materials.During the course of my Phd.study,I mainly foucus on the ground state and excited state regulation of naphthimide molecules,exploring the optical and magnetic properties of the molecules with different spin multiplicity and its potential applications.Specifically,the main contents are summarized as follows.1.In regulating spin multiplicity of excited state,we focuses on the transition strategy for singlet state and triplet state and investigated the effect of linkers(sp3 oxygen-bridged and carbon-bridged)on boron difluoride diketone and naphthimide luminescent properties.The oxygen-bridged difluoride diketone and the carbon-bridged naphthimide were studied by ultraviolet-visible absorption spectroscopy,steady-state emission spectroscopy,single photon counter,and theoretical calculations.We found that with the increase of the electron electron donating ability,the energy gap beteween S1 state and Ti state reduced.And phosphorescence was enhanced.For the naphthalimide system,when the number of methoxy groups was raised to a certain extent,the carbon-linked unit has a negligible effect on the phosphorescence of the molecule.2.In regulating spin multiplicity of ground state,we focuses on the methods for converting the closed shell compounds into stable open shell compounds,and a strategy for generating persistence radicals was proposed,which converted the close shell naphthalimide molecules to the form of open shell.Using naphthimide as the electron-deficient group,by continuously enhancing the electron donation ability of the donor,electron transfer occured and delocalized on the naphthimide.There is a certain correlation between two electrons after electron transfered.This might be the reason why the radical can be persistence for a long time.We also prepared radicals that were persistence in water.Ultraviolet-visible absorption spectrometer,fluorescence spectrometer,electron paramagnetic resonance spectrometer were used to test optical and magnetic properties.We found that after adding alkali,the color of the solution changed,and a new absorption peak appeared in the long wavelength region accompanied by the appearance of an electron paramagnetic resonance signal which last for moths.3.The impact of the substituent's position and the length of linker on spin multiplicity and optical properties of naphthalimide were examined.Different substitution positions(OAP,MAP,PAP)and linkers(PAPP,MAPP)molecules were synthesized.We discovered that the ortho-,meta-,para-substitution of carbonyl group on the benzene ring has little effect on the absorption spectrum of neutral naphthalimide(?mmax=333 nm).The ortho-substitution one owned the the highest phosphorescence/fluorescence ratio.After adding potassium tert-butoxide,there is a clear difference in the absorption,emission and EPR spectrum of OAP,MAP,PAP which showed that exchange integral can be altered by simply changed the substituent's position.The linking unit changing from one benzene ring to two benzene rings had relatively little effect on the optical and magnetic properties of the naphthalimide.4.We attempt to construct organic ferromagnetic materials based on the preparation of persistence naphthimide radicals.We synthesized three types radicals which naphthalimide and acetophenone not covalently linked(B-type),naphthalimide directly connected to acetophenone(C-type)and a flexible chain between naphthalimide and acetophenone(T-type).Magnetic properties including EPR spectrum and hysteresis loop were tested by EPR spectrometer and SQUD.Obvious hysteresis loop was observed and coercivity of T-type larger than the other suggested that the connecting unit played an important role in ferromagnetism.The flexible connecting unit might affect the intermolecular spin and spin interaction instead of intramolecular spin interaction.