Effect Of Geometrical Deformation Of Copper Porphyrins On Electronic Structure And Performances Of Cu Ion

The allosteric effect of metalloproteinases has a decisive effect on its function.The artificial simulation and production application of allosteric effect have become the first choice of scientists in the field of functional complexes.In this paper,two types of the wave-and saddle-type copper porphyrins as catalysts with continuously varying distortions are selected and synthesized.The distortion degree of these nonplanar macrocycles is effectively adjusted by continuously changing the two strap lengths,and the electronic structure of the central ion is adjusted by the geometric changes of the N₄core;the electrochemical performance and reaction mechanism of the above-mentioned catalysts were systematically explored from the aspects of spectroscopy,electrochemistry,single crystal structure,electron paramagnetic resonance,single-point-energy,etc.,The structural comparison of the current two series reveals the influence and rule of the macrocycle changes in geometry on the spectral,paramagnetic and electrocatalytic performances.The work of this thesis includes the following contents in detail:1、In synthesis aspect,two types of non-planar copper porphyrins,wave-type and saddle-type,were synthesized with the help of the strapped strategy of connecting two alkyl chains on the four meso-position phenyl groups of the porphyrin.Four wave copper porphyrins 1-Cu-w,2-Cu-w,3-Cu-w and 4-Cu-w were newly synthesized in this research by fully absorbing the advantages in Adler-Longo and Lindsey methods.The four wave copper porphyrins continuously varied in distortion degree,and have been systematically characterized and analyzed through NMR,HR-MS,UV-vis and other technologies.2、In structure aspect,the single crystals of wave copper porphyrins were obtained from the chloroform/methanol diffusion system.Single crystal analysis showed that the strap of alkyl chains caused non-planar continuous changes of porphyrins and core contraction.With the contraction,the core diameter(L_NN)gradually decreased,and the shortening of straps and the small diameter of copper ions promoted the porphyrin core contracts.3、In electrocatalysis aspect,the ability of two types of non-planar copper porphyrins to electrocatalyze the reduction of protons to hydrogen evolution in 0.5 M H₂SO₄ was followed.The results show that the electrocatalytic HER performance of title copper porphyrins is significantly different with the distortion of the macrocycle.In the wave copper porphyrin series,2-Cu-w has the better electrocatalytic HER performance than other three;while in the saddle copper porphyrin series,the electrocatalytic performance of 1-Cu-s is relatively best,and the performance of saddle-type copper porphyrins HER is generally better than that of wave-type copper materials.4、In spectroscopy aspect,the UV-Vis spectral trend of the wave-type copper porphyrinsis similar to that of the saddle-type ones,and both show a discontinuous red-shift trend with continuous changes in distortion,such as the maximum value of Soret band from2-Cu-w to 1-Cu-w displays a red-shift of 21 nm;while the value from 2-Cu-s to 1-Cu-s only shows a red-shift of 9 nm.This is because the distortion of the ring causes the core to contract,which is derived from changes in the ground state energy of the molecule.5、In magnetic aspect,the spin density change of copper in non-planar copper porphyrins was tested by paramagnetic resonance spectroscopy.The signal intensity of 1-Cu-s at g_⊥branch is obviously differentfrom that of 2-Cu-s to 4-Cu-s in the same system.The 75.8%spin density of d_x~2-_y~2 orbital in 1-Cu-s is much larger than those in other three,and the covalent component of Cu-N_p is accordingly smaller than those in others.This is because the core contraction caused by the ring deformation strongly squeezes the d_x~2-_y~2 orbital of the central metal speciesfrom the equatorial direction,and the octahedral coordination geometry of the central metal ion transforms into a tetrahedral form.6、In orbital energy aspect,the single-point energy of the saddle copper porphyrin was calculated by using the DFT method.It is found that all the changes in 3d orbital energy only occur between 2-Cu-s and 1-Cu-s,there is an obvious"jump",and the change from 4-Cu-s to2-Cu-s is negligible,The changes in energy E_d and charge C_d only involve orbital d_x~2-_y~2 and d_xy in the equatorial direction.This change is considered to be a beneficial change caused by the Push effect in the equatorial direction caused by non-planarity.This thesis studies the effect of the non-planar distortion of metalloporphyrin on its spectral,paramagnetic and electrocatalytic performances.The results show that the significance of the macrocyclic distortion lies in the changes in the coordination geometry of the complexes and the changes in the corresponding energy levels of the metal.The highly deformation of copper porphyrin results in a reversal of the frontier orbitals of the porphyrin ring and copper ions in energy,which makes it easier for electrons flow from macrocycle to the 3d_x~2-_y~2SOMO orbital of central copper ions,thereby showing better electrocatalytic HER performance.The results provide valuable experimental and theoretical support for how to design a catalyst for the HER reaction and how to improve the electrocatalytic performance by adjusting the geometry of metal complexes.