Following the Metalation Process of Protoporphyrin IX with Metal ...

Received: January 18, 2011 

Revised: February 22, 2011 

Published: March 22, 2011 

ARTICLE 

pubs.acs.org/JPCC 

Following the Metalation Process of Protoporphyrin IX with Metal 

Substrate Atoms at Room Temperature 

Ruben Gonzalez-Moreno, †,‡ Carlos Sanchez-Sanchez, ‡ Marta Trelka, § Roberto Otero, § Albano Cossaro, || 

Alberto Verdini, || Luca Floreano, || Marta Ruiz-Bermejo, ^ Aran García-Lekue, 3 Jose Angel Martín-Gago, ‡,^ 

and Celia Rogero* ,† 

† 

Centro de Física de Materiales (CSIC-UPV/EHU), Materials Physics Center MPC, San Sebastian, Spain 

‡ 

Instituto de Ciencia de Materiales de Madrid (ICMM CSIC), Madrid, Spain 

§ 

Instituto Nicolas Cabrera and Instituto Madrile~no de Estudios Avanzados en Nanociencia (IMDEA-NANO), Universidad Autonoma 

de Madrid, Madrid, Spain 

Laboratorio TASC, Istituto Officina dei Materiali (CNR-IOM), Trieste, Italy 

^ 

Centro de Astrobiología (CSIC-INTA), Madrid, Spain 

3 

Donostia International Physics Center (DIPC), San Sebastian, Spain 

) 

ABSTRACT: We have studied the in situ coordination reaction 

of porphyrin molecules, particularly protoporphyrin IX 

(H2PPIX), with copper substrate atoms in ultrahigh vacuum 

conditions with a combination of X-ray photoelectron spectroscopy 

and scanning tunneling microscopy. We show that 

these protoporphyrin IX molecules deposited on Cu surfaces, as 

Cu(110) and Cu(100), form metalloprotoporphyrin IX 

(CuPPIX) by incorporation of Cu atoms from the surface 

already at room temperature. We have followed this reaction 

as a function of temperature and we have determined intermediate 

situations at lower temperatures where the physisorbed 

macrocycle rings present a tendency to establish hydrogen 

bonding between molecules. 

’ INTRODUCTION 

The interaction of planar metal complexes, such as porphyrins, 

phthalocyanines, or corroles (tetrapyrrole molecules), with 

surfaces is especially interesting for designing novel catalysts, 

sensors, and other devices. Because of their photophysical 

properties they are good candidates for the construction of 

photonic devices, such as solar cells and organic light diodes. 1,2 

Depending on the required applications, the properties of these 

macrocycles can be tailored, for example, by changing the 

functional groups around the central core or the metal in the 

center of the core. On the other hand, the chemical reactivity of 

the metal core may affect the performance of the application 

devices, for example, by rapid oxidation of the metal, which 

makes it necessary to work with passivated molecules, or by loss 

of the metal by interaction with the surfaces. 3 An alternative 

procedure for handling with these metalomolecules is to start 

with nonmetalated molecules (free molecules) and metalate 

them directly on a surface. The incorporation of selected metal 

atoms into porphyrins and phthalocyanines on the surface, 

4 14 

also called metalation process, represents an advantage against 

the direct sublimation of metalomolecules. 4 14 The routes 

reported in the literature for surface-mediated metalation in 

ultrahigh vacuum (UHV) conditions involve evaporation of 

the metal atoms by vapor deposition in the appropriate stoichiometry 

before or after the molecular deposition, usually followed 

by annealing of the system formed by the substrate molecule 

metal atoms. 4 14 Interestingly, in none of the reported cases was 

the formation of complexes with the substrate metal atoms 

detected, although such a mechanism would simplify the surface 

synthesis of metalloporphyrins and could likely improve some of 

their properties. Moreover, since the metal core and the substrate 

atoms are of the same nature, the molecule substrate contact 

can be enhanced. Metalation with the substrate has been 

suggested but it has never been proven so far. In this work we 

demonstrate that surface metalation takes place when the protoporphyrin 

IX (H2PPIX) molecule is deposited on Cu substrates. 

Depending on the chosen central metal atom, metalloprotoporphyrin 

IX molecules form biological complexes that are 

essential for life, for example, hemoglobin (Fe), which is responsible 

for oxygen transport in animals, and chlorophyll (Mg), which 

governs energy conversion in the photosynthesis process. 15,16 

r 2011 American Chemical Society 6849 dx.doi.org/10.1021/jp200533a | J. Phys. Chem. C 2011, 115, 6849–6854

The Journal of Physical Chemistry C ARTICLE 

Figure 1. (a) Top and (B) side views of the DFT-optimized ball-andstick 

model of H2PPIX. 

The latter feature is one of the main reasons why this family of 

molecules is investigated within the context of photoluminescence 

applications. The H2PPIX molecule is the nonmetalated 

version of this family of molecules, where two hydrogen atoms 

replace the central metal one. Its structure is almost planar and 

the central macrocycle is surrounded only by short methyl and 

ethenyl groups and two propionic acids (Figure 1). 

In this work we use X-ray photoelectron spectroscopy (XPS) 

to investigate the chemical changes observed in H2PPIX when 

the molecule is interacting directly with metal surfaces, as 

Cu(110) and Cu(100). These surfaces have been chosen as 

models for further studies on more realistic ones for applications, 

as they could be metallic oxides. We study the transition from the 

physisorbed molecular configuration to the chemisorbed one as a 

function of the temperature. Thus, we follow the coordination 

reaction with the substrate atoms, demonstrating that, already at 

room temperature, H2PPIX molecules adsorbed on Cu surfaces 

can form Cu-protoporphyrin IX (CuPPIX) in strongly bound 

self-assembled monolayers (SAMs), as confirmed by scanning 

tunneling microscopy (STM) images. 

’ EXPERIMENTAL DETAILS 

Growth of Molecules. The growth of the molecular films is 

performed in UHV, with a base pressure of


Figure 2. N1s core-level XPS peaks of (A) bulk reference H2PPIX molecules; (B) H2PPIX evaporated on Cu(100) at 160 K and annealed to RT; (C) 

H2PPIX evaporated on Cu(110) at 200 K and annealed to RT; (D) H2PPIX evaporated on Cu(110) at 200 K and annealed at 573 K for 3 min; (E) 

H2PPIX evaporated on Cu(110) at 263 K; (F, G) H2PPIX evaporated on Cu(110) at 200 K (F, monolayer; G, low coverage); and (H) reference 

molecule in solution in DMCO. 

Figure 2 A shows the N1s core level peak of the powder 

H2PPIX molecule used as reference and the best fit obtained. 

The spectrum shows two equivalent components as expected for 

the pristine molecule with the two nonequivalent N atoms, 

iminic at 397.8 eV and pyrrolic at 399.9 eV (47% and 53% of 

the total intensity, respectively). The line shape of N 1s changes 

completely when the molecules are deposited on the copper 

substrates. Figure 2 panels B and C show the N 1s core level 

measured on Cu(100) and Cu(110) substrates, respectively, 

after evaporation of H2PPIX at low temperature and the 

subsequent anneal at RT (the same result is obtained directly 

evaporating at RT, although with much lower sticking of the 

molecule). In both cases the intensity of the component at higher 

binding energy clearly decreases and the spectrum presents an 

intense component at 398.2 eV, slightly shifted with respect to 

the 397.8 eV of the iminic groups. 

The origin of this new line shape can be explained as the result 

of the reaction of the four N atoms with the Cu substrate atoms 

forming a coordination bond; that is, metalation. In fact, this 

component is not at the same position of the iminic N in the 

reference (we remark that it is not possible to have molecules 

with the four N atoms in an iminic conformation). Its energy 

position is consistent with the nitrogen binding energy reported 

for other copper porphyrins. 21 Compared to other bulk 

metalloporphyrins, 10,22 the energy position for the CuPPIX film 

is slightly lower although compatible with them, if we take into 

account two effects related to the planar geometry of the 

molecule and the submonolayer thickness: (i) substrate charge 

transfer and (ii) a more efficient screening of the final core hole. 

In some cases, the first stage of the metalation is witnessed by the 

appearance of a small component at 399.1 eV. This component is 

attributed to deprotonated polypyrroles, that is, macrocycles that 

have lost one H atom, 23 and it is an intermediate step before the 

coordination reaction. No variation of the Cu photoemission 

spectra was detected, because of the very low surface density of 

incorporated Cu atoms even when our measurements are 

performed at grazing incidence. 

The feasibility of in situ metalation of preadsorbed metal-free 

tetrapyrroles with vapor-deposited metal atoms was initially 

demonstrated for Fe 13,14 and extended later for other metals, 

such as Ce, Zn, Co, or Ni. 5 8,24 For some of them, like Fe and Co, 

the reaction proceeds also at RT. For others, like Zn, 8 the 

reaction requires elevated temperatures (above 500 K). On the 

basis of density functional theoery (DFT) calculations of the 

activation barriers, Cu and Zn were proposed to react with 

porphyrins at elevated temperatures. 8 In the present case, we 

observed no significant changes either in the position or in the 

shape of the core level after an annealing beyond room temperature. 

Figure 2 D shows the spectrum of the molecules absorbed 

on Cu(110) and measured after an annealing of the system at 573 

6851 dx.doi.org/10.1021/jp200533a |J. Phys. Chem. C 2011, 115, 6849–6854


Figure 3. O 1s core level XPS peaks of H2PPIX, evaporated on (A) 

Cu(110) at 200 K and (B) Cu(100) at 160 K. 

K (same behavior is observed for the other crystal face). At higher 

temperature, the molecule starts to decompose. In fact, the signal 

of the O 1s core level disappears and new components in the C 1s 

core level appear at lower binding energies that are related to 

Cu C interactions. Therefore, contrary to the theoretical predictions 

calculated for added adatoms, the H2PPIX molecules 

metalate with the Cu substrate atoms already at RT. Moreover, 

we have observed that this process starts at even lower temperatures 

. When the evaporation is performed with the substrate held 

at 263K (see Figure 2 E), the N 1s core level presents one 

relevant component centered at 398.2 eV, which is related to the 

metalated component rather than to the iminic groups. Another 

component is visible at 399.9 eV that might be entirely attributed 

to the pyrrolic N. This double component assignment would 

suggest an intermediate situation, with coexisting free and 

metalated molecules. In fact, similar evidence was reported for 

the metalation of tetraphenylporphyrin (H2TPP) on Ag(111) by 

evaporation of Zn 4,8 where, at RT, the coexistence of three 

species was reported: (i) free molecules, (ii) metalloporphyrins, 

and (iii) an intermediate species where the Zn atoms were 

coordinated although the pyrrolic N H bonds were preserved. 

However, such a simplified decomposition of the spectrum in 

Figure 2E is in contrast with the molecular stoichiometry, since it 

would indicate an excess of the pyrrolic component with respect 

to the iminic one for the population of the intact metal-free 

molecules. 

In order to understand the origin of this apparently unbalanced 

component, we study the behavior of these molecules 

when they just “land” at LT, just after the deposition. Figure 2 F 

shows a high-resolution spectrum of N 1s core level after the 

evaporation of a submonolayer of H2PPIX on Cu(110) with the 

substrate at 200 K. The intensity of the iminic component almost 

disappears and the spectrum presents an intense component at 

400.1 eV, together with a small deprotonated component at 

399.1 eV and an even fainter component at 397.9 eV (this 

component is relatively larger for very low coverage). Apart from 

the slightly larger binding energy (þ0.2 eV), the energy of the 

former component would be compatible with most of the N 

atoms in a pyrrolic-like configuration. This might imply that the 

molecule surface interaction mediates the formation of a 

Figure 4. (A, B) N 1s and (C, D) O 1s core-level XPS peaks of ZnPPIX, 

(A, C) evaporated on Cu(110) at 220 K and (B, D) annealed to RT. 

zwitterionic phase of almost all molecules where the H atoms 

from the carboxylic acid groups migrate to the center of the 

pyrrole rings. 3 

To check the possible occurrence of this change of molecular 

charge state, we measured the XPS spectra from carboxylic 

groups of the molecule after evaporation. Figure 3 shows the 

O 1s core level spectra measured on both samples, Cu(110) and 

Cu(100), at low temperature. Both spectra can be fitted with 

three components, centered at 532.9, 531.8, and 530.9 eV. The 

components at 532.9 and 531.8 eV correspond to the two 

nonequivalent O atoms in the carboxylic acid group, CdO and 

C—OH, respectively, and the one at 530.9 eV corresponds to the 

oxygen atoms in the deprotonated COO group. 25 27 Thus, 

although we have detected a partial deprotonation of the 

carboxylic group at low temperature, its amount is not large 

enough to account for the dominant pyrrolic-like component in 

the N 1s core level around 400 eV. 

The hypothesis of migration of H atoms from the carboxylic 

groups to the central core was proposed by Rienzo et al. 3 for the 

adsorption of zinc protoporphyrin (ZnPtP) on TiO2 (110). In 

this work, the authors suggested that the strong interaction of 

ZnPtP with the oxide surface induces the ejection of Zn atoms 

from the central core and the subsequent occupation with two H 

atoms probably comes from the carboxylic anchor groups. In 

order to check whether this mechanism can be operative on a 



Figure 5. STM images of H2PPIX, (A) after evaporation on Cu(110) at 

200 K (100 100 nm 2 with a zoom of an individual molecule) and (B) 

after annealing to 300 K (5 5nm 2 ). 

copper substrate, we have performed comparative experiments 

with ZnPtP molecules deposited on the Cu(110) surface. 

Figure 4 panels A and C show the N 1s and O 1s core levels 

measured after evaporation of a submonolayer of ZnPtP on 

Cu(110) at LT (220 K). In the N 1s core level at LT, we observe 

for Cu(110) the same double peak result that Rienzo et al. 3 

obtained at RT on TiO 2 (110). However, at LT the O 1s core 

level presents a very low degree of deprotonation of the 

carboxylic group. When the analysis is done after the annealing 

to RT, deprotonation of the carboxylic group is completed 

(Figure 4 D), although at this temperature we observed only 

the metalated molecule, with no signal in the pyrrolic N region 

(Figure 4 B). Therefore, even when the deprotonation of the 

carboxylic group takes place and it is completed at RT, the high 

intensity of the component at around 400 eV in the N 1s core 

level cannot be related only to formation of the zwitterionic 

phase. 

An alternative explanation, which fits all our experimental 

evidences, is the formation of hydrogen-bond interactions between 

H in the carboxylic, methyl and/or ethenyl groups and N 

in the tetrapyrrole ring among surrounding molecules. For 

isonicotinic acid (where each molecule contains a single N 

atom), it has been reported by XPS that two N components 

occur in the N 1s core level that are separated by 1.7 eV. 28 This 

core-level shift is associated with hydrogen bonding between the 

carboxylic group of one molecule and the nitrogen of the 

pyridine ring of the next (this shift between the H-bonded 

nitrogen and the non-H-bonded N atoms is even higher, 1.9 

eV, for picolinic acid, which presents the same chemical formula 

but a different arrangement of atoms in the molecule). 29 This 

head-to-tail hydrogen bonding does not yield deprotonation of 

the carboxylic group and is known from X-ray crystallography 

studies to connect the isonicotinic acid molecules in infinite 

chains in the solid state. 28 30 This mechanism might also apply 

to the present case, as favored by the planar orientation of the 

molecules, large size of the hole in the center of the macrocycle, 

and flexibility of the bonds of the propionic acids. For comparison, 

we performed a reference experiment consisting of dissolving 

H2PPIX in a solvent, particularly DMSO. Figure 2 H shows 

the N 1s core level of the reference sample (check the Experimental 

Details section for specifics). It presents two components at 

binding energies of 399.9 and 397.8 eV. Also in this case part of the 

iminic N atoms form the H bonding and the carboxylic group is not 

deprotonated, according to the double peak structure observed for 

the O 1s core level. We may conclude that H bonds between N and 

H atoms of adjacent molecules can be formed also by deposition 

from solution, in agreement with the mechanism observed by 

evaporation in UHV. We can speculate that the very low deposition 

rate of H2PPIX favors hydrogen bonding, as was also reported for 

the film growth of isonicotinic acid and its isomers. 31 

Finally, we remark that metalation is possible thanks to the close 

planarity of the molecular structure that allows the tetrapyrrole core 

to stay very close to the surface. Near-edge X-ray absorption fine 

structure (NEXAFS) and STM experiments confirm this assumption 

(a detailed discussion about the adsorption geometry will be the 

object of another work). Figure 5 A shows two STM images 

corresponding to H2PPIX deposited at low temperature on Cu- 

(110). After evaporation at 200 K, the molecules aggregates into a 

large density of small clusters, where molecules mainly lie parallel to 

the surface, as shown in the inset image of an isolated molecule. After 

annealing to RT, the metalation reaction is accompanied by selforganization 

of CuPPIX. Figure 5 B illustrates the organized 

structure observed after annealing to RT. In this molecular arrangement, 

variable-polarization NEXAFS measurements indicate PPIX 

molecules to be oriented with the macrocycle almost parallel to the 

surface. Porphyrin orientation induced by some kind of coordination 

reaction with the Cu substrate atoms has been previously 

reported. 22 Klappenberger et al. 23 discuss the formation of an 

ordered network of molecules mediated by the coordination 

reaction that takes place after evaporation and subsequent annealing 

of the tetrapyridylporphyrins (TPyP) on Cu(111). 23,32 In that case, 

the reaction affected the four peripheral N-pyridyl substituents 

instead of the four N atoms in the central macrocycle, and therefore 

metalation was not involved. 23 ThereasonisthatinTPyPthe 

pyridyl nitrogen atoms are not coplanar with the tetrapyrrole, and 

when the molecules interact with the surface, the central macrocycle 

is too far from the surface to react with it. 23,32 On the contrary, the 

geometry of H2PPIX exhibiting an almost planar configuration 

allows the surface macrocycle interaction. We remark that direct 

metalation with surface atoms has not been reported yet for other 

planar tetrapyrroles (like octaethylporphyrin), possibly because they 

have been mostly studied on Ag(111), 11 wherethelargesizemay 

result in an additional steric barrier. In fact, in UHV, no previous 

work reports such a clear surface metalation of any porphyrin. Only 

for gold substrate in a liquid environment a partial surface coordination 

of tetrapyrrole ring with the substrate was suggested, by 

Katsonis et al., 33 who pointed out that some iminic nitrogen atoms 

react with Au atoms thanks to the strong distortion that tetradodecylporphyrin 

suffers on Au(111). 

’ CONCLUSIONS 

In summary, we show a ready molecule substrate coordination 

reaction at RT leading to metalation of porphyrin molecules 



(H2PPIX) with Cu surface atoms (CuPPIX). From our point of 

view, there are several factors that combine to make this reaction 

possible: (1) the closely planar structure of H2PPIX, which 

allows direct surface tetrapyrrole ring contact; 34 (2) the high 

density of Cu adatoms moving on the crystal surfaces that could 

be involved in the coordination reaction; 10 and (3) the rapid rate 

of incorporation of Cu ions by porphyrin macrocycles 35 and the 

high deprotonation rate at RT. The coordinated porphyrins form 

ordered self-assembled monolayers upon annealing. This highly 

stable porphyrin network is more suitable for applications than 

previously attempts to build SAMs with porphyrins. 

’ AUTHOR INFORMATION 

Corresponding Author 

*Centro de Física de Materiales, Po. Manuel de Lardizabal 5, 

Donostia - San Sebastian, Gipuzkoa E-20018, Spain. Tel (þ34) 

943015804; fax (þ34) 943015800; e-mail celia_rogero@ehu.es. 

’ ACKNOWLEDGMENT 

We acknowledge funding through Spanish research projects 

CSD2007-41, MAT2008-1497, PET2008-109, FIS2010-19609- 

C02-00, and BIO 2007-67523 and intramural project 200960I159. 

C.S.-S. is grateful to Ministerio de Educacion for the AP2005-0433 

FPU grant. C.R. and R.G.-M. acknowledge help from and useful 

discussions with A. Arnau and Enrique Ortega. 

’ REFERENCES 

(1) Maree, C. H. M.; Roosendaal, S. J.; Savenije, T. J.; Schropp, 

R. E. I.; Schaafsma, T. J.; Habraken, F. H. P. M. J. Appl. Phys. 1996, 

80, 3381. 

(2) Harima, Y.; Okazaki, H.; Kunugi, Y.; Yamashita, K.; Ishii, H.; 

Seki, K. Appl. Phys. Lett. 1996, 69, 1059. 

(3) Rienzo, A.; Mayor, L. C.; Magnano, G.; Satterley, C. J.; O’Shea, 

J. N.; Ataman, E.; Schnadt, J.; Schulte, K. J. Chem. Phys. 2010, 132, No. 

084703. 

(4) Gottfried, J. M.; Marbach, H. Z. Phys. Chem. 2009, 223, 53. 

(5) Weber-Bargioni, A.; Reichert, J.; Seitsonen, A. P.; Auw€arter, W.; 

Schiffrin, A.; Barth, J. V. Phys. Chem. C 2008, 112, 3453. 

(6) Kretschmann, A.; Walz, M.-M.; Flechtner, K.; Steinr€uck, H.-P.; 

Gottfried, J. M. Chem. Commun. 2007, 568. 

(7) Gottfried, J. M.; Flechtner, K.; Kretschmann, A.; Lukasczyk, Th.; 

Steinr€uck, H.-P. J. Am. Chem. Soc. 2006, 128, 5644. 

(8) Shubina, T. E.; Marbach, H.; Flechtner, K.; Kretschmann, A.; Jux, 

N.; Buchner, F.; Steinr€uck, H.-P.; Clark, T.; Gottfried, J. M. J. Am. Chem. 

Soc. 2007, 129, 9476. 

(9) Buchner, F.; Warnick, K. G.; Wolfle, T.; Gorling, A.; Steinruck, 

H. P.; Hieringer, W.; Marbach, H. J. Phys. Chem. C 2009, 113, 16450. 

(10) Buchner, F.; Flechtner, K.; Bai, Y.; Zillner, E.; Kellner, I.; 

Steinr€uck, H.-P.; Marbach, H.; Gottfried, J. M. J. Phys. Chem. C 2008, 

112, 15458. 

(11) Bai, Y.; Buchner, F.; Wendahl, M. T.; Kellner, I.; Bayer, A.; 

Steinr€uck, H.-P.; Marbach, H.; Gottfried, J. M. J. Phys. Chem. C 2008, 

112, 6087. 

(12) Ecija, D.; Trelka, M.; Urban, C.; de Mendoza, P.; Mateo-Marti, 

E.; Rogero, C.; Martin-Gago, J. A.; Echavarren, A. M.; Otero, R.; Gallego, 

J. M.; Miranda, R. BiochemistryJ. Phys. Chem. C 2008, 112, 8988. 

(13) Auw€arter, W.; Weber-Bargioni, A.; Brink, S.; Riemann, A.; 

Schiffrin, A.; Ruben, M.; Barth, J. V. Chem. Phys. Chem. 2007, 8, 250. 

(14) Buchner, F.; Schwald, V.; Comanici, K.; Steinruck, H. P.; 

Marbach, H. ChemPhysChem 2007, 8, 241. 

(15) Voet, D.; Voet, J. G. Biochemistry, 3rd ed.; John Wiley & Sons 

Inc.: New York, 2004. 

(16) van Grondelle, R.; Dekker, J. P.; Gillbro, T.; Sundstrom, V. 

Biochim. Biophys. Acta 1994, 1, 1187. 

(17) Moulder, J. F.; Stickle, W. F.; Sobol, P. E.; Bomben, K. D. 

Handbook of X-ray Pholoelectron Spectroscopy; PerkinElmer Corp.: 

Waltham, MA, 1992. 

(18) Cossaro, A.; Floreano, L.; Verdini, A.; Casalis, L.; Morgante, A. 

Phys. Rev. Lett. 2009, 103, No. 119601. 

(19) Floreano, L.; Cossaro, A.; Gotter, R.; Verdini, A.; Bavdek, G.; 

Evangelista, F.; Ruocco, A.; Morgante, A.; Cvetko, D. J. Phys. Chem. C 

2008, 112, 10794. 

(20) Horcas, I.; Fernandez, R.; Gomez-Rodriguez, J. M.; Colchero, 

J.; Gomez-Herrero, J.; Baro, A. M. Rev. Sci. Instrum. 2007, 78, No. 

013705. 

(21) Gulino, A.; Fragala, I.; Scamporrino, E.; Vitalini, D. J. Phys. 

Chem. C 2007, 111, 14125. 

(22) Mele, G.; Del Sole, R.; Vasapollo, G.; Marci, G.; Garcia-Lopez, 

E.; Palmisano, L.; Coronado, J. M.; Hernandez-Alonso, M. D.; Malitesta, 

C.; Guascito, M. R. J. Phys. Chem. B 2005, 109, 12347. 

(23) Klappenberger, F.; Weber-Bargioni, A.; Marschall, M.; 

Schiffrin, A.; Auw€arter, W.; Barth, J. V. J. Chem. Phys. 2008, 129, No. 

214702. 

(24) Chen, M.; Feng, X.; Zhang, L.; Ju, H.; Xu, Q.; Zhu, J.; Gotffried, 

J. M.; Ibrahim, K.; Qian, H.; Wang, J. J. Phys Chem. C 2010, 114, 9908. 

(25) Stepanow, S.; Strunskus, T.; Lingenfelder, M.; Dmitriev, A.; 

Spillmann, H.; Lin, N.; Barth, J. V.; W€oll, Ch.; Kern, K. J. Phys. Chem. B 

2004, 108, 19392. 

(26) Ca~nas-Ventura, M. E.; Klappenberger, F.; Clair, S.; Pons, S.; 

Brune, H.; Kern, K.; Strunskus, T.; W€oll, C.; Fasel, R.; Barth, J. V. 

J. Chem. Phys. 2006, 125, No. 184710. 

(27) Dmitriev, A.; Spillmann, H.; Stepanow, S.; Strunskus, Th.; 

W€oll, Ch.; Seitsonen, A. P.; Lingenfelder, M.; Lin, N.; Barth, J. V.; Kern, 

K. Chem. Phys. Chem. 2006, 7, 2197. 

(28) O’Shea, J. N.; Schnadt, J.; Bru1hwiler, P. A.; Hillesheimer, H.; 

Martensson, N. J. Phys. Chem. B 2001, 105, 1917. 

(29) O’Shea, J. N.; Luo, Y.; Schnadt, J.; Patthey, L.; Hillesheimer, H.; 

Krempasky, J.; Nordlund, D.; Nagasono, M.; Br€uhwiler, P. A.; 

Martensson, N. Surf. Sci. 2001, 486, 157. 

(30) Takusagawa, F.; Shimada, A. Acta Crystallogr. 1976, B32, 1925. 

(31) Schnadt, J.; O’Shea, J. N.; Patthey, L.; Schiessling, J.; 

Krempasky, J.; Shi, M.; Martensson, N.; Br€uhwiler, P. A. Surf. Sci. 

2003, 544, 74. 

(32) Shi, Z.; Lin, N. J. Am. Chem. Soc. 2009, 131, 5376. 

(33) Katsonis, N.; Vicario, J.; Kudernac, T.; Visser, J.; Pollard, M. M.; 

Feringa, B. L. J. Am. Chem. Soc. 2006, 128, 15537. 

(34) Bai, Y.; Buchner, F.; Kellner, I.; Schmid, M.; Vollnhals, F.; 

Steinruck, H. P.; Marbach, H.; Gottfried, J. M. New J. Phys. 2009, 11, No. 

125004. 

(35) Dempsey, B., et al. In Haematin Enzymes; Falk, J. E., Lemberg, 

R., Morton, R. K., Eds.; Pergamon Press: New York, 1959; pp 29 37

Following the Metalation Process of Protoporphyrin IX with Metal ...

Create successful ePaper yourself

Delete template?

Save as template?