Phthalocyanines, a class of macrocyclic, square planar molecules, are extensively studied as semiconductor materials for chemical sensors, dye-sensitized solar cells, and other applications. Pthalocyanines offer high tunability of their electronic and optical properties through the choice of metal center atom; nearly all transition metals and many other heavier elements can reside at the relatively stable phthalocyanine square planar center. The electronic transport properties also depend on the orientation and order of molecular crystals and their chemical environment, making phthalocyanines particularly useful for chemical sensing. In this study, we use angular dependent near-edge x-ray absorption fine structure (NEXAFS) as a quantitative probe of the orientation and electronic structure of H 2 -, Fe-, Co-, and Cu-phthalocyanine molecules thin films. NEXAFS measurements at both the carbon and nitrogen K-edges reveal that phthalocyanine films deposited on sapphire have upright molecular orientations, while films up to 50 nm thick deposited on gold substrates are composed of molecules with prostrate orientations. Although great similarity is observed in the carbon and nitrogen K-edge NEXAFS spectra recorded for the films composed of prostrate molecules, the H 2 -phthalocyanine exhibits the cleanest angular dependence due to its purely out-of-plane !* resonances at the absorption onset. In contrast, metal-phthalocyanines have a small in-plane resonance superimposed on this !* region that is due to a transition into molecular orbitals interacting with the 3d x 2 -y 2 empty state. Complementary NEXAFS spectra recorded at the metal L-edges for the prostrate films reveal dramatic variations in the angular dependence of specific resonances for the Cu-phthalocyanines compared with the Fe-, and Cophthalocyanines. The Cu L 3,2 edge exhibits a strong in-plane resonance, due to its b 1g LUMO with d x 2 -y 2 character at the Cu center. Conversely, the Fe-and Co-phthalocyanine L 3,2 edges have strong out-ofplane resonances arising primarily from LUMO states with e g symmetry and d xz and d yz character at the metal center.Introduction:Thin films of organometallic phthalocyanines (PCs) are versatile device materials-with demonstrated applications in dye-sensitized solar cells 1 , organic transistors 2-6 , chemiresistive gas-sensors [7][8][9][10] , and organic light emitting diodes 11 . The broad success in implementing this class of planar, organic molecules is a direct consequence of the tunability and sensitivity of their electronic and optical properties with gap energies corresponding to visible wavelengths. In thin film configurations, specified device performance is achieved through a combination of structural selectivity, and the choice of metal center atom. Nearly all transition metals and many heavier elements can reside at the relatively stable square planar center of the phthalocyanine. The metal atom interacts with the ligand, giving rise to a coordination complex with distinct electronic structure.Building a clea...