Soft X-Ray Absorption Spectra of the Lithium Phthalocyanine Radical

Abstract

In near edge X-ray absorption fine structure (NEXAFS) spectra of carbon (C) and nitrogen (N) K-edge regions were measured for the stable radical compound lithium phthalocyanine (LiPc). The observed spectra were compared with those of metal free Pc ( H 2 Pc ), copper Pc (CuPc), and zinc Pc (ZnPc). The spectral features in the C K-edge region of LiPc were different from those of other Pcs in the low photon energy region. An additional peak around 283.5 eV was observed only in the spectrum of LiPc. On the other hand, the spectral features of these MPcs in the N K-edge region were similar and did not show a corresponding extra peak. These results were explained by the patterns of molecular orbitals of these Pcs and the selection rules of X-ray absorption in the localized core-hole picture. The extra peak observed in the C K-edge region is assigned to the excitation from C1s to the highest occupied molecular orbital (HOMO), which is only singly occupied due to the radical nature of the phthalocyanine ring. Group-theoretical consideration indicated that the transition from N1s to the HOMO is not allowed, and this explains the lack of an extra peak at the N K-edge.

Molecular Orientation and Ordering during Initial Growth of Copper Phthalocyanine on Si(111)

“…Each spectrum has absorption features consistent with previous reports 14,15 , although the relative intensities for these features are angle-dependent. The first four sharp absorption peaks (A, B, C, D) are assigned to excitations from N 1s core level to individual π* states, and the broad absorption features at the higher photon energy side correspond to transitions to * states.…”

Electronic structure of pristine CuPc: Experiment and calculations

“…Red circles on the curve indicate specific photon energies, at which representative valence band PES spectra were taken. As it was already shown for CuPc thin films [27,33] and for SnPc [34] the rather sharp peaks marked by numbers 5, 11, 16, and 18 in the top panel in Fig. 3 are due to the 1s-p * transitions at nitrogen sites in different chemical environments.…”

“…Analogously, the sharp peaks labeled with the same A, B, C letters for N 1s excitation threshold in Fig. 4b, in the energy interval between 398 and 405 eV, can be attributed to the N 1s-p * excitations [27,33,34].…”

High-resolution inner-shell excitation spectroscopy of H2-phthalocyanine

“…The family of phthalocyanine ͑Pc͒ molecules, for example, represents one of the most promising materials for organic devices, as they may form ordered thin films and as their electrical and optical properties can be altered by substitution of functional groups and/or of the central metal atom. [4][5][6][7][8][9][10][11][12] Thus, Pc molecules are of potential use in a wide variety of applications; consequently, there is a strong motivation for detailed studies of electronic, structural, and morphological properties of thin Pc films.…”