Electronic structure of copper phthalocyanine: An experimental and theoretical study of occupied and unoccupied levels

Ab Initio Modeling of Mixed-Dimensional Heterostructures: A Path Forward

Understanding the electronic structure of mixed-dimensional heterostructures is essential for maximizing their application potential. However, accurately modeling such interfaces is challenging due to the complex interplay between the subsystems. We employ a computational framework integrating first-principles methods, including GW, density functional theory (DFT), and the polarizable continuum model, to elucidate the electronic structure of mixed-dimensional heterojunctions formed by free-base phthalocyanines and monolayer molybdenum disulfide. We assess the impact of dielectric screening across various scenarios, from isolated molecules to organic films on a substrate-supported monolayer. Our findings show that while polarization effects cause significant renormalization of molecular energy levels, band energies and alignments in the most relevant setup can be accurately predicted through DFT simulations of the individual subsystems. Additionally, we analyze orbital hybridization, revealing potential pathways for interfacial charge transfer. This study offers new insights into hybrid inorganic/organic interfaces and provides a practical computational protocol suitable for scaled-up studies.

Insightful understanding of charge transfer processes in metalated phthalocyanines

Marcus electron transfer theory coupling with quantum-mechanics (QM) calculations was applied to study the hole mobilities of a series of metalated phthalocyanine molecular crystals. The effect of metal on the...

Study of Photoregeneration of Zinc Phthalocyanine Chemiresistor after Exposure to Nitrogen Dioxide

In this work, we present a complex study of photoregeneration of a zinc phthalocyanine (ZnPc) sensor by illumination from light-emitting diodes (LEDs). It includes an investigation of photoregeneration effectivity for various wavelengths (412–723 nm) of incident light carried out at sensor operating temperatures of 55 °C. It is demonstrated that the efficiency of photoregeneration is increasing with a decrease in the light wavelength. In the region of longer wavelengths (723–630 nm), the regeneration degree (RD) was low and ranged from 12% to 15%. In the region of shorter wavelengths (518–412 nm), the RD rose from 35% for 518 nm to 94% for 412 nm. The efficiency of photoregeneration is also shown to be higher in comparison with the temperature regeneration efficiency. In order to understand the chemism of photoregeneration processes, the electrical measurements are supplemented with Raman and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) studies. The spectroscopic results showed that nitrogen dioxide bonds to the Zn atom in ZnPc in the form of NO2− and NO−, i.e., partial decomposition of NO2 molecules occurs during the interaction with the surface. NAP-XPS spectra proved that light illumination of the ZnPc surface is essential for almost complete desorption of NOx species. At the same time, it is demonstrated that in case of long-time exposure or exposure of a ZnPc chemiresistor with a high concentration of NO2, the oxygen, released due to the NO2 decomposition, slowly but irreversibly oxidizes the layer. This oxidation process is most probably responsible for the sensor deactivation observed in sensor experiments with high NO2 concentrations. Based on these studies, the mechanism of nitrogen dioxide interaction with zinc phthalocyanine both under LED illumination and in dark conditions is proposed, and a special method for the sensor operation called “constant exposure dose” is established.

Electronic Structure of Metallophthalocyanines, MPc (M = Fe, Co, Ni, Cu, Zn, Mg) and Fluorinated MPc

We compute the electronic structure and optical excitation energies of metal-free and transition-metal phthalocyanines (H₂Pc and MPc for M = Fe, Co, Ni, Cu, Zn, Mg) using density functional theory with optimally tuned range-separated hybrid functionals (OT-RSH). We show that the OT-RSH approach provides photoemission spectra in quantitative agreement with experiments as well as optical band gaps within 10% of their experimental values, capturing the interplay of localized d-states and delocalized π-π* states for these organometallic compounds. We examine the tunability of MPcs and H₂Pc through fluorination, resulting in quasi-rigid shifts of the molecular orbital energies by up to 0.7 eV. Our comprehensive data set provides a new computational benchmark for gas-phase phthalocyanines, significantly improving upon other density-functional-theory-based approaches.

Pentacene/perfluoropentacene bilayers on Au(111) and Cu(111): impact of organic-metal coupling strength on molecular structure formation

As crucial element in organic opto-electronic devices, heterostructures are of pivotal importance. In this context, a comprehensive study of the properties on a simplified model system of a donor-acceptor (D-A) bilayer structure is presented, using ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED) and normal-incidence X-ray standing wave (NIXSW) measurements. Pentacene (PEN) as donor and perfluoropentacene (PFP) as acceptor material are chosen to produce bilayer structures on Au(111) and Cu(111) by sequential monolayer deposition of the two materials. By comparing the adsorption behavior of PEN/PFP bilayers on such weakly and strongly interacting substrates, it is found that: (i) the adsorption distance of the first layer (PEN or PFP) indicates physisorption on Au(111), (ii) the characteristics of the bilayer structure on Au(111) are (almost) independent of the deposition sequence, and hence, (iii) in both cases a mixed bilayer is formed on the Au substrate. This is in striking contrast to PFP/PEN bilayers on Cu(111), where strong chemisorption pins PEN molecules to the metal surface and no intermixing is induced by subsequent PFP deposition. The results illustrate the strong tendency of PEN and PFP molecules to mix, which has important implications for the fabrication of PEN/PFP heterojunctions.

Transistor properties of salen-type metal complexes

Schiff base complexes derived from salicylaldehyde and ethylene-, propylene-, and trans-1,2-cyclohexane-diamines exhibit p-channel transistor properties. The Cu complexes are open-shell compounds, but the oxidation and the hole transport occur at the highest occupied molecular orbital, where the singly occupied molecular orbital (SOMO) does not participate in conduction. Although Ni complexes tend to show larger mobilities than Cu complexes owing to the molecular planarity, the presence of SOMO is not harmful to the transistor properties.

Heteromolecular Bilayers on a Weakly Interacting Substrate: Physisorptive Bonding and Molecular Distortions of Copper-Hexadecafluorophthalocyanine

Heteromolecular bilayers of π-conjugated organic molecules on metals, considered as model systems for more complex thin film heterostructures, are investigated with respect to their structural and electronic properties. By exploring the influence of the organic-metal interaction strength in bilayer systems, we determine the molecular arrangement in the physisorptive regime for copper-hexadecafluorophthalocyanine (F₁₆CuPc) on Au(111) with intermediate layers of 5,7,12,14-pentacenetetrone and perylene-3,4,9,10-tetracarboxylic diimide. Using the X-ray standing wave technique to distinguish the different molecular layers, we show that these two bilayers are ordered following their deposition sequence. Surprisingly, F₁₆CuPc as the second layer within the heterostructures exhibits an inverted intramolecular distortion compared to its monolayer structure.

Study of C K-Edge High Energy Resolution Energy-Loss Near-Edge Structures of Copper Phthalocyanine and Its Chlorinated Molecular Crystals by First-Principles Band Structure Calculations

High energy resolution energy-loss near-edge structures (ELNES) at the carbon K-edge of copper phthalocyanine (CuPc) and its chlorinated molecular crystals were observed using electron energy-loss spectroscopy combined with a scanning transmission electron microscope equipped with a monochromator. The ELNES spectra were investigated using first-principles band structure calculations with a core-hole introduced into the 1s orbitals of the nonequivalent C atoms. The calculated spectra including half a core-hole were consistent with the experimental spectra. The spectral features could be interpreted in terms of the different contributions of the partial density of states (PDOS) of nonequivalent C atoms with different transition energies depending on the site. The core-hole effects were also discussed using the spatial distribution of unoccupied states and PDOSs, which revealed site-dependent core-hole effects, where a C atom with a strong spatial distribution intensity of the unoccupied states in the ground state (GS) are susceptible to the core-hole effects. The spectral changes due to chlorination of the CuPc molecule were mainly attributed to an increase of the threshold energy of the C atoms bonded to chlorine, and the influence of the change in the PDOS by chlorination was not significantly large.

Generalized single excitation configuration interaction: an investigation into the impact of the inclusion of non-orthogonality on the calculation of core-excited states

In this paper, we investigate different non-orthogonal generalizations of the configuration interaction with single substitutions (CIS) method and their impact on the calculation of core-excited states.

Metal phthalocyanines interaction with Co mediated by a moiré graphene superlattice

The assembling of metal phthalocyanines on the rippled moiré superlattice of graphene/Ir(111) intercalated with one Co layer is driven by the site-dependent polarization field induced by the incommensurate graphene-Co interface. We have performed an X-ray absorption and photoemission study to unveil the role of the metallic centers and of the organic ligands in the molecule-Co interaction process mediated by graphene. Notably, we consider different electronic molecular orbitals, i.e. phthalocyanines with Cu and Mn metallic ions. The spectroscopic response suggests almost unaltered CuPc molecular states upon adsorption, and the rippled graphene carpet decouples completely the electronic interaction between the molecules and the Co layer, while a slight hybridization is present for MnPcs. MnPc molecules, trapped in the valleys of the moiré graphene superlattice, slightly intermix, through the orbitals protruding out of the molecular plane, with the underlying Co, while the organic ligands are almost unaltered. Graphene acts as an interlayer and mediates the interaction between metal phthalocyanines and the metallic substrate, preventing a strong chemical intermixing and enabling the assembly of almost unaltered molecules, preserving their electronic/magnetic state.

Two-photon photoemission spectroscopy of unoccupied electronic states at CuPc/PTCDA/Ag(1 1 1) interfaces

The unoccupied electronic structure of stacked layers of copper(II)phthalocyanine (CuPc) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on Ag(1 1 1) has been investigated by means of two-photon photoemission (2PPE). We find a rich electronic structure comprising at least five unoccupied electronic states which we identify based on their energetic position and their dispersion in momentum space. More specifically, we observe the first and the second image-potential states of the modified Ag(1 1 1) surface, as well as the metal-organic interface state (IS) inherent to the PTCDA/Ag(1 1 1) interface. Moreover, two additional molecular features are observed for the CuPc/PTCDA/Ag(1 1 1) system which we attribute to an unoccupied molecular orbital (LUMO  +  2) of CuPc. The 2PPE intensity of the IS exhibits a pronounced dependence on the pump photon energy, which closely follows the optical absorption of the outer molecular layer. This strongly points to charge transfer from the optically excited molecules to the interface state.

Dielectric Screening Meets Optimally Tuned Density Functionals

A short overview of recent attempts at merging two independently developed methods is presented. These are the optimal tuning of a range-separated hybrid (OT-RSH) functional, developed to provide an accurate first-principles description of the electronic structure and optical properties of gas-phase molecules, and the polarizable continuum model (PCM), developed to provide an approximate but computationally tractable description of a solvent in terms of an effective dielectric medium. After a brief overview of the OT-RSH approach, its combination with the PCM as a potentially accurate yet low-cost approach to the study of molecular assemblies and solids, particularly in the context of photocatalysis and photovoltaics, is discussed. First, solvated molecules are considered, with an emphasis on the challenge of balancing eigenvalue and total energy trends. Then, it is shown that the same merging of methods can also be used to study the electronic and optical properties of molecular solids, with a similar discussion of the pros and cons. Tuning of the effective scalar dielectric constant as one recent approach that mitigates some of the difficulties in merging the two approaches is considered.

Energy-Level Alignment of a Hole-Transport Organic Layer and ITO: Toward Applications for Organic Electronic Devices

2,2',6,6'-Tetraphenyl-4,4'-dipyranylidene (DIPO-Ph₄) was grown by vacuum deposition on an indium tin oxide (ITO) substrate. The films were characterized by atomic force microscopy as well as synchrotron radiation UV and X-ray photoelectron spectroscopy to gain an insight into the material growth and to better understand the electronic properties of the ITO/DIPO-Ph₄ interface. To interpret our spectroscopic data, we consider the formation of cationic DIPO-Ph₄ at the ITO interface owing to a charge transfer from the organic layer to the substrate. Ionization energy DFT calculations of the neutral and cationic species substantiate this hypothesis. Finally, we present the energetic diagram of the ITO/DIPO-Ph₄ system, and we discuss the application of this interface in various technologically relevant systems, as a hole-injector in OLEDs or as a hole-collector interfacial layer adjacent to the prototypical OPV layer P3HT:PCBM.

Molecular Crystal Engineering: Tuning Organic Semiconductor from p-type to n-type by Adjusting Their Substitutional Symmetry

Focusing on the bottleneck of molecularly engineered organic semiconductors, a breakthrough is made to tune the electronic properties of organic semiconductors from p-type to n-type by using fluorinated metal phthalocyanines as examples. The experimentally observed p-type to n-type transition characteristics of single-crystal field-effect devices result from a combination of extrinsic and intrinsic properties of materials with different fluoridation substitution.

CASSCF-based explicit ligand field models clarify the ground state electronic structures of transition metal phthalocyanines (MPc; M = Mn, Fe, Co, Ni, Cu, Zn)

Multireference electronic structure methods are used to assign ground state electronic configurations for a series of metallophthalocyanines. Ligand orbital occupancies remain constant across the period and are consistent with a formal 2– charge on the ligand. The d electron configurations of some metallophthalocyanines are straightforward and can be unambiguously assigned, (dxy)2(dxz,dyz)2,2( [Formula: see text])2([Formula: see text])n, with n = 2, 1, 0, respectively, for ZnPc, CuPc, and NiPc. Controversies over ground state electronic structure assignments for other metallophthalocyanines arise due to multiple complicating factors: accidental near-degeneracies, environmental effects, and different ligand field models used in interpreting experimental spectra. We demonstrate that explicit ligand field models provide more reliable and consistent interpretations of experimental data than implicit, parameterized alternatives. On this basis, we assign gas-phase electronic ground states for MnPc, (dxy)2(dxz,dyz)1,1([Formula: see text])1 and CoPc, (dxy)2(dxz,dyz)2,2([Formula: see text])1, and show that the ground state of FePc cannot be resolved to a single state, with two near-degenerate states that are likely spin-orbit coupled: (dxy)2(dxz,dyz)1,1( [Formula: see text])2 and (dxy)2(dxz,dyz)2,1([Formula: see text])1. Remaining differences between computational predictions and experimental observations are small and may be ascribed primarily to environmental effects but are also partly due to incomplete modelling of electron correlation.

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

We describe a model for interpreting XAFS spectra of metal phthalocyanines. The near edge spectra are reproduced in a full potential approach.

Dynamics of copper-phthalocyanine molecules on Au/Ge(001)

Spatially resolved current-time scanning tunneling spectroscopy combined with current-distance spectroscopy has been used to characterize the dynamic behavior of copper-phthalocyanine (CuPc) molecules adsorbed on a Au-modified Ge(001) surface. The analyzed CuPc molecules are adsorbed in a "molecular bridge" configuration, where two benzopyrrole groups (lobes) are connected to a Au-induced nanowire, whereas the other two lobes are connected to the adjacent nanowire. Three types of lobe configurations are found: a bright lobe, a dim lobe, and a fuzzy lobe. The dim and fuzzy lobes exhibit a well-defined switching behavior between two discrete levels, while the bright lobe shows a broad oscillation band. The observed dynamic behavior is induced by electrons that are injected into the LUMO+1 orbital of the CuPc molecule. By precisely adjusting the tip-molecule distance, the switching frequency of the lobes can be tuned accurately.

Reliable energy level alignment at physisorbed molecule-metal interfaces from density functional theory

A key quantity for molecule-metal interfaces is the energy level alignment of molecular electronic states with the metallic Fermi level. We develop and apply an efficient theoretical method, based on density functional theory (DFT) that can yield quantitatively accurate energy level alignment information for physisorbed metal-molecule interfaces. The method builds on the "DFT+Σ" approach, grounded in many-body perturbation theory, which introduces an approximate electron self-energy that corrects the level alignment obtained from conventional DFT for missing exchange and correlation effects associated with the gas-phase molecule and substrate polarization. Here, we extend the DFT+Σ approach in two important ways: first, we employ optimally tuned range-separated hybrid functionals to compute the gas-phase term, rather than rely on GW or total energy differences as in prior work; second, we use a nonclassical DFT-determined image-charge plane of the metallic surface to compute the substrate polarization term, rather than the classical DFT-derived image plane used previously. We validate this new approach by a detailed comparison with experimental and theoretical reference data for several prototypical molecule-metal interfaces, where excellent agreement with experiment is achieved: benzene on graphite (0001), and 1,4-benzenediamine, Cu-phthalocyanine, and 3,4,9,10-perylene-tetracarboxylic-dianhydride on Au(111). In particular, we show that the method correctly captures level alignment trends across chemical systems and that it retains its accuracy even for molecules for which conventional DFT suffers from severe self-interaction errors.

Ultrafast Electron Transfer at Organic Semiconductor Interfaces: Importance of Molecular Orientation

Much is known about the rate of photoexcited charge generation in at organic donor/acceptor (D/A) heterojunctions overaged over all relative arrangements. However, there has been very little experimental work investigating how the photoexcited electron transfer (ET) rate depends on the precise relative molecular orientation between D and A in thin solid films. This is the question that we address in this work. We find that the ET rate depends strongly on the relative molecular arrangement: The interface where the model donor compound copper phthalocyanine is oriented face-on with respect to the fullerene C60 acceptor yields a rate that is approximately 4 times faster than that of the edge-on oriented interface. Our results suggest that the D/A electronic coupling is significantly enhanced in the face-on case, which agrees well with theoretical predictions, underscoring the importance of controlling the relative interfacial molecular orientation.

Spectroscopic fingerprints of work-function-controlled phthalocyanine charging on metal surfaces

The electronic character of a π-conjugated molecular overlayer on a metal surface can change from semiconducting to metallic, depending on how molecular orbitals arrange with respect to the electrode's Fermi level. Molecular level alignment is thus a key property that strongly influences the performance of organic-based devices. In this work, we report how the electronic level alignment of copper phthalocyanines on metal surfaces can be tailored by controlling the substrate work function. We even show the way to finely tune it for one fixed phthalocyanine-metal combination without the need to intercalate substrate-functionalizing buffer layers. Instead, the work function is trimmed by appropriate design of the phthalocyanine's supramolecular environment, such that charge transfer into empty molecular levels can be triggered across the metal-organic interface. These intriguing observations are the outcome of a powerful combination of surface-sensitive electron spectroscopies, which further reveal a number of characteristic spectroscopic fingerprints of a lifted LUMO degeneracy associated with the partial phthalocyanine charging.

Outer-valence Electron Spectra of Prototypical Aromatic Heterocycles from an Optimally Tuned Range-Separated Hybrid Functional

Density functional theory with optimally tuned range-separated hybrid (OT-RSH) functionals has been recently suggested [Refaely-Abramson et al. Phys. Rev. Lett.2012, 109, 226405] as a nonempirical approach to predict the outer-valence electronic structure of molecules with the same accuracy as many-body perturbation theory. Here, we provide a quantitative evaluation of the OT-RSH approach by examining its performance in predicting the outer-valence electron spectra of several prototypical gas-phase molecules, from aromatic rings (benzene, pyridine, and pyrimidine) to more complex organic systems (terpyrimidinethiol and copper phthalocyanine). For a range up to several electronvolts away from the frontier orbital energies, we find that the outer-valence electronic structure obtained from the OT-RSH method agrees very well (typically within ∼0.1–0.2 eV) with both experimental photoemission and theoretical many-body perturbation theory data in the GW approximation. In particular, we find that with new strategies for an optimal choice of the short-range fraction of Fock exchange, the OT-RSH approach offers a balanced description of localized and delocalized states. We discuss in detail the sole exception found—a high-symmetry orbital, particular to small aromatic rings, which is relatively deep inside the valence state manifold. Overall, the OT-RSH method is an accurate DFT-based method for outer-valence electronic structure prediction for such systems and is of essentially the same level of accuracy as contemporary GW approaches, at a reduced computational cost.

Understanding the adsorption of CuPc and ZnPc on noble metal surfaces by combining quantum-mechanical modelling and photoelectron spectroscopy

Phthalocyanines are an important class of organic semiconductors and, thus, their interfaces with metals are both of fundamental and practical relevance. In the present contribution we provide a combined theoretical and experimental study, in which we show that state-of-the-art quantum-mechanical simulations are nowadays capable of treating most properties of such interfaces in a quantitatively reliable manner. This is shown for Cu-phthalocyanine (CuPc) and Zn-phthalocyanine (ZnPc) on Au(111) and Ag(111) surfaces. Using a recently developed approach for efficiently treating van der Waals (vdW) interactions at metal/organic interfaces, we calculate adsorption geometries in excellent agreement with experiments. With these geometries available, we are then able to accurately describe the interfacial electronic structure arising from molecular adsorption. We find that bonding is dominated by vdW forces for all studied interfaces. Concomitantly, charge rearrangements on Au(111) are exclusively due to Pauli pushback. On Ag(111), we additionally observe charge transfer from the metal to one of the spin-channels associated with the lowest unoccupied π-states of the molecules. Comparing the interfacial density of states with our ultraviolet photoelectron spectroscopy (UPS) experiments, we find that the use of a hybrid functionals is necessary to obtain the correct order of the electronic states.

Theoretical study of near-edge X-ray absorption fine structure spectra of metal phthalocyanines at C and N K-edges

The inner shell excitation of CuPc, NiPc, and H(2)Pc phthalocyanines at both C and N K-edges has been investigated theoretically by density functional theory calculations. The selected molecules allow one to study the effect on the spectra of the presence and the nature of the atom in the central cavity of the macrocycle. The individual characteristics of the spectra can be rationalized in terms of the position of the unequivalent C and N atomic sites, showing that sensible changes are present in the spectral features deriving from the N atoms directly bound to the atom at the center of the Pc macrocycle. The minor variations present in the spectral C 1s profiles of the phthalocyanines reflect the little perturbation experienced by the peripheral atomic sites.

Commensurate registry and chemisorption at a hetero-organic interface

We present evidence for a partly chemisorptive bonding between single monolayers of copper-II-phthalocyanine (CuPc) and 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) that are stacked on Ag(111). A commensurate registry between the two molecular layers and the substrate, i.e., a common crystallographic lattice for CuPc and PTCDA films as well as for the Ag(111) surface, indicates that the growth of the upper layer is dominated by the structure of the lower. Photoemission spectroscopy clearly reveals a gradual filling of the lowest unoccupied molecular orbital of PTCDA due to CuPc adsorption, which proves the chemisorptive character.

Copper-phthalocyanine based metal-organic interfaces: the effect of fluorination, the substrate, and its symmetry

Metal-organic interfaces based on copper-phthalocyanine monolayers are studied in dependence of the metal substrate (Au versus Cu), of its symmetry [hexagonal (111) surfaces versus fourfold (100) surfaces], as well as of the donor or acceptor semiconducting character associated with the nonfluorinated or perfluorinated molecules, respectively. Comparison of the properties of these systematically varied metal-organic interfaces provides new insight into the effect of each of the previously mentioned parameters on the molecule-substrate interactions.

Modeling the interactions of phthalocyanines in water: from the Cu(II)-tetrasulphonate to the metal-free phthalocyanine

A quantum and statistical study on the effects of the ions Cu(2+) and SO(3)(-) in the solvent structure around the metal-free phthalocyanine (H(2)Pc) is presented. We developed an ab initio interaction potential for the system CuPc-H(2)O based on quantum chemical calculations and studied its transferability to the H(2)Pc-H(2)O and [CuPc(SO(3))(4)](4-)-H(2)O interactions. The use of the molecular dynamics technique allows the determination of energetic and structural properties of CuPc, H(2)Pc, and [CuPc(SO(3))(4)](4-) in water and the understanding of the keys for the different behaviors of the three phthalocyanine (Pc) derivatives in water. The inclusion of the Cu(2+) cation in the Pc structure reinforces the appearance of two axial water molecules and second-shell water molecules in the solvent structure, whereas the presence of SO(3)(-) anions implies a well defined hydration shell of about eight water molecules around them making the macrocycle soluble in water. Debye-Waller factors for axial water molecules have been obtained in order to examine the potential sensitivity of the extended x-ray absorption fine structure technique to detect the axial water molecules.

The interface bonding and orientation of a quinonoid zwitterion

We have investigated the interaction and orientation of a strongly dipolar zwitterionic p-benzoquinonemonoimine-type molecule, with a large intrinsic dipole of 10 Debye, on both conducting and on polar insulating substrates. Specifically, we deposited (6Z)-4-(butylamino)-6-(butyliminio)-3-oxocyclohexa-1,4-dien-1-olate C(6)H(2)([horiz bar, triple dot above]NHR)(2)([horiz bar, triple dot above]O)(2) where R = n-C(4)H(9), on both gold and ferroelectric lithium niobate surfaces. An influence of both transient and static electric dipoles on the zwitterionic adsorbate has been observed. For adsorption on gold, we find that the molecule bonds to the surface through the nitrogen atoms, forming films that remain fairly uniform down to thicknesses in the 1 nm range. Adsorption of this zwitterionic compound from solution on insulating, periodically poled ferroelectric lithium niobate substrates, showed preferential adsorption on one type of ferroelectric domain. For both gold and the lithium niobate substrates, the zwitterion adopts a preferential orientation with the plane of its "C(6) core" along the surface normal. This simplified geometry of strong dipole alignment provides a symmetry simplification allowing better identification of the vibrational modes responsible for Frank-Condon scattering revealed in the fine spectroscopic signature in the photoemission spectrum.