Local environment of metal ions in phthalocyanines: K-edge X-ray absorption spectra

Abstract

We report a detailed study of the K-edge X-ray absorption spectra of four transition metal phthalocyanines (MPc, M = Fe, Co, Cu and Zn). We identify the important single and multiple scattering contributions to the spectra in the extended energy range and provide a robust treatment of thermal damping; thus, a generally applicable model for the interpretation of X-ray absorption fine structure spectra is proposed. Consistent variations of bond lengths and Debye Waller factors are found as a function of atomic number of the metal ion, indicating a variation of the metal-ligand bond strength which correlates with the spatial arrangement and occupation of molecular orbitals. We also provide an interpretation of the near edge spectral features in the framework of a full potential real space multiple scattering approach and provide a connection to the local electronic structure.

Evolution of Zn(II) single atom catalyst sites during the pyrolysis-induced transformation of ZIF-8 to N-doped carbons

“…3d transitions were seen, consistent with Zn 2+ in ZnTPP having a 3d 10 configuration. Above the absorption edge, three main features are seen, labelled as A, B and C. Since most metal porphyrins share the same features in their K-edge XAS spectra [37], features A, B, and C in ZnTPP can be assigned with reference to FeTPPCl [38]. Feature A (9661.7 eV) is a Zn 1s to Zn 4p z transition with simultaneous ligand to metal charge transfer.…”

“…Feature C (9672.6 eV) involves multiple scattering https://engine.scichina.com/doi/10.1016/j.scib.2020.06.020 paths, and serves as a general fingerprint of local Zn environments with different Zn-N bonding distances. Reproduction of the spectral features A, B, C requires at least five coordination shells (up to the third shell C atoms in the benzene rings of ZnTPP) [37]. In other words, any distortions from the square planar ZnN 4 geometry in ZnTPP structure would result in an energy shift or intensity change of all these features.…”

Atomically dispersed Ni in cadmium-zinc sulfide quantum dots for high-performance visible-light photocatalytic hydrogen production

“…Figure S6 simulated the XANES of NiS x ( x = 6, 4, and 3) complexes to study their symmetrical dependency. The shoulder near 8348 eV appears in the sixfold coordinated NiS 6 octahedron ( O h ), fourfold coordinated NiS 4 tetrahedra ( T d ), threefold coordinated NiS 3 triangular pyramid, and the trigonal planar complex ( C 3v ), but not in the square planar complexes ( C 4v ) ( 32 ). For NiS 6 O h symmetry, the e g ( d z 2 and d x 2 −y 2 ) mainly contributes to the electric dipole and quadrupole transitions, whereas for the NiS 4 T d , it mainly comes from the t 2 g ( d xy , d yz , and d xz ) (fig.…”

Linear dichroism in the NEXAFS spectra of n-alkane crystalline polymorphs

“…This linear dichroism (LD) can be used to study molecular orientation for n-alkanes and other molecular species and can help clarify spectroscopic assignments. [14][15][16][17][18][19][20][21][22][23] The morphology of an n-alkane sample and the orientation of n-alkane chains within this sample are affected by conditions that include n-alkane chain length, [24] substrate temperature during growth, and the sample preparation method (e.g. solution casting versus epitaxial growth by physical vapour deposition).…”