Magnetic and Surface Properties of Metallophthalocyanines (M= Cu, Fe)

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Magnetic and Surface Properties of Metallophthalocyanines (M= Cu, Fe) Grafted Polyethylene Alena Reznickova, Martin Orendac, Erik Cizmár, Ondrej Kvitek, Petr Slepicka, Zdenka Kolska, and Vaclav Svorcik J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b10984 • Publication Date (Web): 27 Dec 2017 Downloaded from http://pubs.acs.org on December 30, 2017

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The Journal of Physical Chemistry Reznickova et al., Magnetic and surface properties of metallophthalocyanines (M= Cu, Fe) grafted polyethylene

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Magnetic and Surface Properties of Metallophthalocyanines (M= Cu, Fe) Grafted Polyethylene Alena Reznickova,*,† Martin Orendac,‡ Erik Cizmar,‡ Ondrej Kvitek,† Petr Slepicka,† Zdenka Kolska,┴ and Vaclav Svorcik† †

Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague,

Czech Republic ‡

Faculty of Science, P.J. Safarik University, Park Angelinum 9, 04013 Kosice, Slovakia

┴

Faculty of Science, J.E. Purkyne University, 400 96 Usti nad Labem, Czech Republic

ABSTRACT: To employ advantageous tunable magnetic properties of metal phthalocyanines (Pcs) in practical devices it is necessary to bind them to solid substrates. A simple method to bind Cu(II) and Fe(III) sulfonated phthalocyanines on plasma treated surface of polyethylene (PE) is proposed. Formation of reactive centers (radicals) on the PE surface after the plasma treatment was observed in electron-spin resonance (ESR) spectra at 330 mT and 350 mT. The signal at 350 mT disappears after grafting of the Pcs, which suggests the radical is spent on formation of a chemical bond. Successful grafting of Pcs was also confirmed by X-ray photoelectron spectroscopy and SEM-EDS measurements. In UV-Vis spectra Q and B bands typical for the π-π interaction in Pcs were observed at 620 and 340 nm, respectively. Splitting of the Q band occured due to reduction in symmetry of the peripherally substituted Pcs. Interestingly, lower concentration of CuPc solution during grafting process lead to higher amount grafted to the surface. In the case of FePc the optimum grafting concentration is higher. The ESR spectra of PE samples with grafted FePc were similar to the bulk Pcs with the high-spin state (S=5/2) of d5 Fe(III) ions.

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*Corresponding author: E-mail address: [email protected]; Tel.: +420 220 445 159; Fax: +420 220 310 337

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INTRODUCTION Phthalocyanines (Pcs) are planar aromatic macrocycles constituted of four isoindole units linked together via nitrogen atoms. The inner and outer positions of the fused benzene ring are also called α- and β-positions, respectively. Their 42 π-electrons are distributed over 32 carbon and 8 nitrogen atoms, but the delocalization of electrons can be detected mainly on the inner ring, which is constituted by 16 atoms and 18 π-electrons, while the outer benzene rings retain their electric behavior.1,2 Due to the above-mentioned properties the metallophthalocyanines (MPcs) are well known for their semiconducting behavior besides of their thermal and chemical stability.3,4 Pcs are commonly used in optical and magnetic equipment such as optical switches, liquid crystals, nonlinear optics, single molecule magnets and optical communication and storage devices.5-7 Pcs are regarded as special organic systems in a way that they possess extensive opportunities in adjusting of their physico-chemical properties over a wide range of parameters involving either substitution of different metal atoms (Cu, Fe, Co, Zn, Ni, Mn etc.) into the ring or modification of peripheral and axial functional groups.3,5,8,9 Among various candidates of MPcs, phthalocyanine-tetrasulfonic acid tetrasodium salt was found to be of high significance due to its high water solubility in ambient atmosphere and its ability to be deposited easily from aqueous solution, which makes the possible device fabrication process economical as well as ecological.4 Metallophthalocyanines can be bound covalently or non-covalently to a substrate thanks to the high π- electron delocalization.10 Chemical and physical properties of thin Pcs films depend on the particular substrate: i.e. metal,11 semiconductor9,12 or polymer.6,13 Polymers in their pristine state usually do not exhibit the surface properties which are needed for the above-mentioned applications. Therefore, surface modification techniques to transform these inexpensive materials into highly valuable products are required. Common surface modification techniques include treatment by flame, plasma, photons, electron beams, ion beams, X-rays, and γ-rays.14 Considering compatibility with current thin-film based plastic electronic and optoelectronic technologies, and reliability of manufacturing and usage, there is high potential value in for example copper phthalocyanine (CuPc), that can be produced on an industrial scale and readily processed in thin films both for solar energy and molecular electronics.15,16 In addition, Pcs have high application potential in quantum computing and data storage. Studies of spin dynamics in thin crystalline layers of CuPc deposited on Kapton substrate revealed their spin–spin relaxation time is long enough for performing qubit operations in a wide temperature range.6 Recent studies of relaxation phenomena in the high-spin Fe(III)-based complex showed a substantial increase of the spin–spin relaxation time in high magnetic fields.17 This result indicates the possibility of realization of qubits from magnetic ions with higher spins under appropriate experimental conditions. Consequently, it may be ACS Paragon Plus Environment

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desirable to compare magnetic behavior of CuPc and Fe(III) sulfonated phthalocyanine (FePc grafted on a polymeric substrate). This paper continues in our previous study where we have investigated structural and magnetic response of Cu(II) sulfonated phthalocyanine (CuPc) grafted on plasma treated polyethylene (PE) surface. Our previous study has shown the lower is the concentration of CuPc the higher is the magnetic response.18 In this paper we have investigated surface and magnetic properties of CuPc grafted PE at even lower concentrations (i.e. 2·10-5, 1·10-5 and 5·10-6 mol L−1) and also properties of Fe(III) sulfonated phthalocyanine (FePc) grafted PE. Magnetic measurements of the CuPc and FePc grafted PE were conducted from nominally 2 to 50 K.

EXPERIMENTAL SECTION Materials, apparatus and procedures High density polyethylene (PE; 0.95 g cm−3; Mw= 4·105 g·mol−1) in the form of 40 µm thick foils (supplied by Granitol Ltd., CZ) was used in this study. In the first step, the samples were treated in Ar+ plasma on Balzers SCD 050 device. The treatment time was 120 s, the discharge power was 8.3 W, gas purity was 99.997 %, flow rate 0.3 L·s-1, pressure 10 Pa, electrode distance 50 mm and its area 48 cm2, chamber volume approx. 1,000 cm3, plasma volume 240 cm3 and the treatment was accomplished at laboratory temperature. The parameters of treatment (120 s exposure time, 8.3 W power) were chosen since these led to the most pronounced changes of polymer surface in our previous experiments.19 In the second step, immediately after the plasma treatment, the samples were immersed into water solution of (i) Cu(II) phthalocyanine-3,4´,4´´,4´´´-tetra-sulfonic acid tetrasodium salt (CuPc; C32H12CuN8O12S4·4·Na; Mw= 984.3 g mol−1; Sigma Aldrich Corp., US), and (ii) Fe(III) phthalocyanine-4,4′,4′′,4′′′-tetrasulfonic acid, compound with oxygen monosodium salt hydrate (FePc; C32H15FeN8O14S4Na·x H2O; Mw= 942.6 g mol−1; Sigma Aldrich Corp., US), for 1 or 24 h (see Figure 1). Plasma treated PE was subsequently grafted with (a) 2·10-5, (b) 1·10-5 and (c) 5·10-6 mol L−1 metal phthalocyanines (labelled as aCuPc, bCuPc, cCuPc or aFePc,bFePc, cFePc). The samples were then rinsed in distilled water and dried under N2 flow. Samples were kept under laboratory conditions. Analytical methods Differential ultraviolet-visible (UV–Vis) absorption spectra were recorded using a Perkin-Elmer Lambda 25 spectrophotometer (Perkin Elmer Inc., US). The samples were kept in 1 cm quartz cell. Reference spectrum of pristine PE was subtracted from the spectra of modified samples. Data were 3 ACS Paragon Plus Environment


collected in the wavelength region of 350 to 800 nm with 1 nm step at the scan rate of 240 nm·min1

. The error of the values of optical absorption was below 1.5 %. Concentrations of C(1s), O(1s), S(2p), Cu(2p3/2) and Fe(2p3/2) atoms in the modified surface

layer were measured by X-ray Photoelectron Spectroscopy (XPS). Omicron Nanotechnology ESCAProbe P spectrometer (Omicron Nanotechnology GmbH, DE) was used to measure photoelectron spectra (typical error of 5 %). XPS analysis was performed at a pressure of 2·10-8 Pa. The exposed and analyzed area was 2x3 mm2. X-ray source was monochromatic at 1486.7 eV with step size of 0.05 eV, take off angle was 0° with respect to the sample surface normal. The spectra evaluation was carried out by CasaXPS software. The morphology of the prepared structures was investigated using scanning electron microscopy (SEM, Tescan Lyra dual beam microscope; Tescan Ltd., CZ). Element mapping was performed using an energy dispersive X- ray spectroscopy (EDS, analyzer X-MaxN, 20 mm2 SDD detector, Oxford Instruments plc, UK). The samples were attached by carbon conductive tape to avoid sample charging. SEM-EDS and SEM measurements were carried out using accelerating voltages 10 kV and 2 kV, respectively. The samples were coated by sputtered thin layer of gold (20 nm). Exposed and analyzed area was 10x10 µm2. Electrokinetic analysis (zeta potential) of all samples was performed by SurPASS Instrument (Anton Paar GmbH, AT). Samples were studied inside the adjustable gap cell (0.001 mol L−1 KCl, measured eight times, pH = 6.3, room temperature, error of 5 %). For zeta potential determination the streaming current method and Helmholtz-Smoluchowski equation were used. Electron-spin resonance (ESR) was studied in an X-band spectrometer Bruker ELEXYS II E500 (Bruker Corp., US). Each studied sample of 4 cm2 nominal area was folded in a quartz ampoule and placed in a cryostat in the spectrometer resonator. The measurements were performed in 2 -50 K temperature range at 9.4 GHz frequency. The power of the high-frequency signal was tuned to 0.6325 mW for studies at 2 K and 0.07962 mW for temperature sweeps to maximize signal-to-noise ratio and avoid saturation effects. Modulation technique with 100 kHz modulation frequency and amplitude of 1 Gauss was used for signal detection for measurements at 2 K and 4 Gauss for temperature sweeps. The contribution of the background represented predominantly by the cryostat itself was studied in a separate run and was subtracted from the total signal.

RESULTS AND DISCUSSION The plasma activated PE surface was grafted with Cu(II) and Fe(III) sulfonated phthalocyanines for 1 and 24 h and its surface and magnetic properties were investigated. The two metals were chosen due to their different electronic structure. In on our previous studies we observed higher magnetic response ACS Paragon Plus Environment

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at lower CuPc concentrations, thus three even lower concentrations of MPcs solutions (2·10-5, 1·105

and 5·10-6 mol L−1) were chosen for the present study.18 The results are divided into two

subsections related to (i) physico-chemical analysis of surface properties of pristine and modified PE and (ii) investigation of magnetic response of the prepared samples. Surface properties Phthalocyanines present intense π-π bands in the visible (Q band; 600-700 nm) and UV (B or Soret band; near 340 nm) spectral regions.20 Q and B bands correspond to transitions to the lowest excited-state orbitals from the highest occupied orbital (for the Q band) and from the low occupied orbitals (for the B band). Differential UV-Vis spectra of plasma treated PE subsequently grafted with metallophthalocyanine solutions with different concentrations of CuPc and FePc (2·10-5, 1·10-5 and 5·10-6 mol L−1; resp. aMPc, bMPc and cMPc) for 1 and 24 h are shown in Figure 2. In Figure 2 B and Q band are marked and clearly visible. The strongest absorption peaks of CuPc and FePc lie between 610-680 nm and 640-700 nm, respectively. The exact position of these bands depends on the particular structure, metal complexation, and peripheral substituents. For peripherally substituted MPcs, the degenerate Q band shows some splitting due to the reduction in symmetry.3, 21, 22

The highest overall absorption was found in the case of samples grafted with cCuPc and cFePc

for 1 h. The position of B and Q band of the composite films remained consistent with the increasing metallophthalocyanine concentration, but the peaks grew gradually stronger.4 The most pronounced Q band has been observed on samples PE/120/bCuPc/24 h and PE/120/aFePc/24 h. The substrates grafted with FePc showed no Q band except for samples grafted with aFePc. This could be due to the contribution of the polymer to a reduced transmission, or due to the greater amount of aggregation the phthalocyanines undergo in thin films, which in turn leads to greater optical limiting.23 It should be noted that despite the apparently small disparities in the structures of the phthalocyanines, the UV-Vis spectra of CuPc and FePc are quite different. These discrepancies can be caused by: (i) different electron-metal structure, (ii) the orientation and (iii) coverage of the phthalocyanines on the substrate.24 The UV-Vis absorption after 1 h of grafting is higher than after 24 h for both the phthalocyanines at each MPc concentration. In conclusion the lowest MPc concentration (in solution) showed the highest UV-Vis absorption. The character of the UV-Vis spectra is most likely associated with the concentration of MPcs on the PE surface. To confirm this XPS and EDS analyses were performed. Atomic concentrations of elements derived from the XPS spectra (C1s, O1s, S2p, Cu2p3/2 and Fe2p3/2) are summarized in Table 1. As was expected the PE surface becomes strongly oxidized after the plasma treatment (oxygen concentration is 22.2 at. %).18,19 After the grafting of CuPc and FePc, the oxygen concentration slightly increases due to grafting of phthalocyanine molecules on the plasma activated 5 ACS Paragon Plus Environment


PE surface. After grafting of the CuPc and FePc solutions (aMPc, bMPc and cMPc) different concentrations of sulfur, copper and iron was observed. These results confirmed the successful binding of MPcs to polymer substrate. For samples grafted with bFePc and cFePc there was no sulfur detected, but trace amounts of sodium were present in the spectra. This result might be connected to different orientation of organic molecules on the PE surface.6,24,25 Table 1 documents increase of metal concentration after 24 h of grafting compared to 1 h of grafting of CuPc or FePc on the plasma treated PE. The typical thickness of the analysed layer of XPS under perpendicular (0°) collection angle is ca 2 nm while in the case of UV-Vis measurements the light beam goes through the bulk of the polymer sample. Therefore, XPS should be more sensitive to changes of the surface properties. To analyze the oxidation states of the metals present on the polymer surface, deconvolution of Cu(2p3/2) and Fe (2p3/2) peaks of PE treated by plasma and grafted with bCuPc and bFePc (PE/120/bMPc/24 h) for 24 h has been performed (see Figure 3). These two samples have been chosen based on UV-Vis spectroscopy and ESR results. Sample grafted with bCuPc for 24 h has the most pronounced Q band and the highest magnetic response (see below). The peak fit of the Cu(2p3/2) revealed two binding energy states at 935.88 and 934.96 eV, which we assign to a Cu(II) state.26 In the NIST database (srdata.nist.gov) binding energy of 935.88 eV corresponds to Cu(II) amide group and 934.96 eV value correlates with Cu(II) sulfate or Cu(II) hydroxide.27-29 The peak fit of the Fe(2p3/2) showed two binding energy states of 711.20 and 709.63 eV. The peak at 713.20 eV is caused by asymmetry in the iron spectra. Binding energies of 709.63 and 711.20 eV can be assigned to iron (II) oxide, iron (III) oxide or its mixture iron (II, III) oxide which correlates with Fe(II) and Fe(III) states.30,31 SEM-EDS analysis was performed to determine morphology and the element mapping of the novel molecular materials. The exposed and analyzed area was 10x10 µm2. EDS maps of plasma treated PE and samples subsequently grafted with bCuPc or aFePc for 24 h are shown in Figure 4. Different colours in Figure 4 represent elements as follows: C (orange), O (dark cyan), S (purple), Cu (red) and Fe (green). The presence of S, Cu and Fe in EDS mapping confirms the grafting of metallophthalocyanine on the surface of plasma treated PE. EDS also revealed that Cu and Fe atoms are homogeneously distributed over the whole PE surface. Concentration of Cu atoms is slightly higher than Fe atoms, which is in good accordance with results obtained from XPS and UV-Vis spectroscopy. SEM analysis of PE grafted with bCuPc or aFePc for 24 h also provides information about the surface morphology (Figure 5). A lamellar structure is apparent, which can be attributed to semicrystalline structure of the polymer, which is typical for Ar+ plasma treated PE.32 No significant difference was found for surface morphology of PE grafted with CuPc or FePc.

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Results of zeta potential determination in Figure 6 confirm the results obtained by the other employed techniques. Plasma treatment leads to change of surface chemistry due to presence of oxygen polar groups on the surface. Therefore the zeta potential changes dramatically compared to pristine PE. Subsequent grafting of MPcs leads to surface chemistry and charge changes as well. More significant zeta potential changes are visible for 1 hour CuPc grafting time. This indicates much more intensive grafting of CuPc compared to FePc and also higher grafted amount of MPc after 1 hour grafting compared to 24 hours. The medium concentration has a great impact on successful grafting as well. In the case of CuPc the lower solution concentration leads to better results. The difference between grafting of CuPc and FePc can be caused by different surface orientation of the molecules which has been observed for other chemical compounds as well.6,24,25 Magnetic properties Magnetic properties of both systems were investigated by ESR, which was conducted from nominally 2 to 50 K. The effect of using different concentrations and grafting times was studied at 2.1 K and for CuPc the results are presented in Figure 7. Similarly as for higher CuPc concentrations studied previously the obtained spectrum consists of three components. The broad one, characteristic for Cu(II) ions spreads from 260 to 380 mT. In addition, two small absorptions with g-factors g = 2.0 (signal I) and g = 1.94 (signal II) were detected at 330 mT and 350 mT, respectively. Both small absorptions can be attributed to radicals created by plasma treatment of PE. Whereas signal I survives for all concentrations and grafting times, signal II is present clearly only for cCuPc. Different behavior of both signals reveals their different role in grafting process. Whereas persistence of signal I suggests that the corresponding radicals are created inside the surface layer determined by plasma penetration and thus do not directly participate grafting. On the other hand, radicals associated with signal II are located on the surface and may be involved in the grafting. The previous study with higher CuPc concentration during grafting showed that the higher signal from grafted CuPc resulted in lower intensity of signal II suggesting its participation in grafting of the CuPc molecules on the surface. However, the presence of signal II only for cCuPc and the comparison of its intensity with the broad component might suggest that concentration of surface radicals II is also decreased by another mechanism during the grafting and CuPc is grafted on other functional groups as well. It should be pointed out, that the intensity of the signal I is neither constant with respect to concentration and grafting time nor correlated with the intensity of the broad component. This behavior has not been clarified yet and will be subject of further studies. The orientation of the CuPc molecules on the surface may reflect the surface order and also depend on the thickness of the deposited layers.33 The CuPc molecules can predominantly order in parallel direction to the PE surface as was observed for some thin layers of CuPc deposited on 7 ACS Paragon Plus Environment


different substrates.34,35 The shape of the broad ESR signal attributed to CuPc molecules does not exhibit an angular dependence (as folded and installed in the sample tube to perform lowtemperature ESR) for all of our samples. It was modelled as an ESR spectrum of powdered sample with gx = 2.047, gy = 2.055, and gz = 2.179 and anisotropic linewidth ∆Bx = 10.7 mT, ∆By = 14.3 mT, ∆Bz = 35.7 mT due to the unresolved hyperfine coupling. The obtained values of g-factor components agree well with previously reported values.36-39 The change of the ESR spectrum with temperature was investigated for bCuPc grafted for 24 h, where the most pronounced response was observed and the results are presented in Figure 8. The integral intensity, obtained by double integration of the ESR spectrum, corresponds to magnetic susceptibility and increases with decreasing temperature similarly as for a paramagnet.40 However, below nominally 5 K a deviation from the aforementioned behavior is detected which might be tentatively attributed to magnetic interactions. Notably, magnetic coupling between transition metal ions and radicals in the order of Kelvins was found in Ref. 41. As for CuPc, magnetic coupling might exist between a radical in PE and magnetic dx2-y2 orbital of Cu(II) ion with exchange path involving π-electrons from the inner ring. Notably, π-electrons in phthalocyanines can mediate exchange interactions even in the order of 100 K.42 However, more data are necessary for clarifying this conjecture. ESR spectra of FePc samples prepared under various conditions are presented in Figure 9, the most pronounced response was found for aFePc grafted for 24 h suggesting that optimum grafting concentration of FePc molecules is higher than that of CuPc. The observed spectrum displays richer structure than for CuPc with strong central resonance at 338 mT and several weak resonance modes located in the 300-360 mT range. Similarly as for CuPc, both signal I and signal II were detected at 330 mT and 350 mT. The contribution of signal II seems to be higher for shorter grafting times, similar behavior was observed for CuPc. The ESR spectra of FePc samples are similar to the bulk material and we need to determine the spin state of Fe(III) ions to be able to simulate the spectrum and to obtain the characteristic crystal-field parameters. For transition-metal phthalocyanines different spin states can be observed for bulk and thin-layer samples due to the restrictions of the crystal field. An intermediate spin-state with strong zero-field splitting can be present instead of the high-spin state for d4-d7 ions in phthalocyanines.43-45 In Fe(III) phthalocyanines and porphyrines an intermediate spin-state is more rare and theoretical calculations suggest the presence of high-spin state (S = 5/2) in porphyrins with O2 ligand coordinated to Fe(III) ions as in the studied FePc samples.46, 47 Our simulations also failed to describe the obtained ESR spectra if other than high-spin state of Fe(III) ions was considered. The high-spin state (S=5/2) of d5 Fe(III) ions is characterized by a very small zero-field splitting and isotropic g-factors (see Ref. 48).


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The best agreement with experimental spectra was obtained for g = 1.987, zero-field splitting parameters D/kB = -0.0105 K, E/D = 0.07 and linewidth ∆B = 3.5 mT. The high-field part of the spectra seems to be broadened in comparison with the simulation and this could be accounted for by some additional anisotropic broadening mechanism. It should be noted that the possible presence of Fe(II) ions might not be detected by X-band ESR due to their typical strong zero-field splitting. Temperature dependence of the ESR spectrum was studied for aFePc grafted for 24 h and is presented in Figure 10. A monotonous decrease of the signal intensity with increasing temperature is the same as in the case of bCuPc grafted for 24 h. The same relative intensity of the components of the spectra is preserved in a wide temperature range confirming the assumption of very small zero-field splitting (keeping the same thermal population of the energy levels defined by the spin hamiltonian).

CONCLUSIONS This paper deals with preparation and characterization of new magnetic surfaces by grafting copper (II) and iron (III) sulfonated phthalocyanines (CuPc, FePc) onto plasma treated PE surface. Three different concentrations of metal phthalocyanines (2·10-5, 1·10-5 and 5·10-6 mol L−1; labelled as a

CuPc, bCuPc, cCuPc or aFePc, bFePc, cFePc) and two grafting times (1 and 24 h) have been

investigated. The most pronounced Q band in the UV-Vis spectra has been observed on samples PE/120/bCuPc/24 h and PE/120/aFePc/24 h, while the highest absorption was found for the samples grafted with cCuPc and cFePc for 1 h. Q band splitting is caused by reduction in symmetry of peripherally substituted MPcs. UV-Vis measurements showed that absorption after 1 h of grafting is higher than after 24 h of grafting for both phthalocyanines at each concentration of MPc. The samples prepared with the lowest metallophthalocyanine concentration (in solution) showed the highest UV-Vis absorption. These results were also supported by elektrokinetic analysis. Differences between XPS results and UV-Vis measurements are caused by analytical depth of the respective spectroscopic methods. Presence of S, Cu and Fe in the XPS spectra and EDS mapping confirms successful grafting of CuPc and FePc on the plasma treated PE. EDS mapping demonstrated that Cu and Fe atoms are homogeneously distributed over the whole PE surface. The analyzed concentration of Cu atoms was slightly higher than Fe atoms, which is in good agreement with XPS, UV-Vis spectroscopy and electrokinetic analysis. ESR studies revealed the presence of two types of radicals, one created in the volume of PE and not involved in the grafting and the second one generated predominantly on the surface which participates the grafting process. In addition, the presence of CuPc and FePc grafted on PE was confirmed, where characteristic parameters for both copper (II) ion with S = ½ and iron (III) ion with S = 5/2 do not differ 9 ACS Paragon Plus Environment


significantly from those in the corresponding bulk compounds. These novel molecular materials could find applications in optoelectronics or in data storage technologies.

AUTHOR INFORMATION Corresponding author (A.R.)* E-mail: [email protected] Telephone: +420 220 445 159 Fax: +420 220 310 337 Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS This work was supported by the Czech Science Foundation (GA CR) under the projects 17-00939S, P108/12/G108 and APVV - 14 – 0073.

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(21) Sanchez-Vergara, M.E.; Garcia-Montalvo, V.; Alonso-Huitron, J.C.; Rodriguez, A.; JimenezSandoval, O. Electrical and optical properties of one-dimensional metallophthalocyanine (M = Fe) thin films grown by thermal evaporation. J. Mater. Sci.: Mater. Electron. 2012, 23, 193199. (22) De la Torre, G.; Vaquez, P.; Agullo-Lopez, F.; Torres, T. Role of structural factors in the nonlinear optical properties of phthalocyanines and related compounds. Chem. Rev. 2004, 104, 3723-3750. (23) Britton, J.; Litwinski, C.; Antunes, E.; Durmus, M.; Chaukea, V.; Nyokong, T. Optical limiting analysis of phthalocyanines in polymer thin films. J. Macromol. Sci. A 2013, 50, 110120. (24) Li, Z.; Lieberman, M. XPS and SERS study of silicon phthalocyanine monolayers: umbrella vs octopus design strategies for formation of oriented SAMs. Langmuir 2001, 17, 4887-4894. (25) Kolská, Z.; Řezníčková, A.; Nagyová, M.; Slepičková Kasálková, N.; Sajdl, P.; Slepička, P.; Švorčík, V. Plasma activated polymers grafted with cysteamine for bio-application. Polym. Degr. Stab. 2014, 101, 1-9. (26) Chusuei, C.C.; Brookshier, M.A.; Goodman, D.W. Correlation of relative X-ray photoelectron spectroscopy shake-up intensity with CuO particle size. Langmuir 1999, 15, 2806-2808. (27) Yoshida, T.; Yamasaki, K.; Sawada, S. X- ray photoelectron spectroscopic study of biuret metal-complexes. Bull. Chem. Soc. Jpn. 1978, 51, 1561-1562. (28) Klein, J.C.; Li, C.P.; Hercules, D.M.; Black, J.F. Decomposition of copper - compounds in Xrays photoelectron spectrometers. Appl. Spectrosc. 1984, 38, 729-734. (29) McIntyre, N.S; Sunder, S.; Shoesmith, D.W.; Stanchell, F.W. Chemical information from XPS- appplication to the analysis of electrode. J. Vac. Sci. Technol. 1981, 18, 714-721. (30) Oku, M.; Hirokawa, K. X-ray photoelectron spectroscopy of Co3O4, Fe3O4, Mn3O4 and related compounds. J. Electron Spectrosc. Relat. Phenom. 1976, 8, 475-481. (31) Mills, P.; Sullivan, J.L. A study of the core level electrons in iron and its 3 oxides by means of X-ray photoelectron spectroscopy. J. Phys. D. 1983, 16, 723-732. (32) Reznickova, A.; Novotna, Z.; Kolska, Z.; Slepickova-Kasalkova, N.; Rimpelova, S.; Svorcik, V. Enhanced adherence of mouse fibroblast and vascular cells to plasma modified polyethylene. Mat. Sci. Eng. C 2015, 52, 259-266. (33) Pasimeni, L.; Segre, U.; Toffoletti, A.; Valli, L.; Marigo, A. EPR study of in-plane anisotropy in the LB films of a Cu(II) [tetra alkoxy carbonyl] phthalocyanine deposited on mylar sheets. Thin Solid Films 1996, 284-285, 655-658.


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dipivaloylmethanate during deposition as an illustration of the capabilities of EPR. Appl. Magn. Reson. 2002, 23, 123-132. (35) Boguslavsky, E.G.; Prokhorova, S.A.; Nadolinny, V.A. Evolution of ordered films of copper phthalocyanine according to EPR data. J. Struct. Chem. 2005, 46, 1014-1022. (36) Harrison, S.E.; Assour, J.M. Relationship of electron spin resonance and semiconduction in phthalocyanines. J. Chem. Phys. 1964, 40, 365-370. (37) Guzy, C.M.; Raynor, J.B.; Symons, M.C.R. Electron spin resonance spectrum of copper-63 phthalocyanine. A reassessment of the bonding parameters. J. Chem. Soc. A 1969, 15, 22992302. (38) Graczyk, A.; Dobkowski, J. EPR studied of complexes of copper phthalocyanine with alimunium chloride. J. Magn. Reson. 1979, 24, 467-474. (39) Finazzo, C.; Calle, C.; Stoll, S.; Van Doorslaer S.; Schweiger, A. Matrix effects on copper(II)phthalocyanine complexes. A combined continuous wave and pulse EPR and DFT study. Phys. Chem. Chem. Phys. 2006, 8, 1942–1953. (40) Chipara, M.I.; Grecu, V.V.; Notingher, P.V.; Romero, J.R.; Chipara, M.D. ESR investigation on ion-beam irradiated polycarbonate. Nucl. Instrum. Meth. B 1994, 88, 418-422. (41) Šoltésová, D.; Vasylets, A.; Čižmár, E.; Botko, M.; Cheranovskii, V.; Starodub, V.; Feher, A. Exchange interaction between TCNQ and transition metal ion mediated by hydrogen bonds in [Mn(phen)(3)](TCNQ)(2)center dot H2O and [Co(phen)(3)] (TCNQ)(2)center dot H2O. J. Phys. Chem. Solids 2016, 99, 182-188. (42) Konarev, D.V.; Nakano, Y.; Khasanov, S.S.; Kuzmin, A.V.; Ishikawa, M.; Otsuka, A.; Yamochi, H.; Saito, G.; Lyubovskaya, R.N. Magnetic and optical properties of layered (Me4P+)[(MO)-O-IV(Pc•3−)]•(TPC)0.5•C6H4Cl2 salts (M = Ti and V) composed of pistacking dimers of titanyl and vanadyl phthalocyanine radical anions. Cryst. Growth Des. 2017, 17, 753–762. (43) Bartolomé, J.; Monton, C.; Schuller, I.K. Magnetism of Metal Phthalocyanines, in Molecular Magnets Physics and Applications; Springer-Verlag, Berlin Heidelberg, DE, 2014. (44) Liao, M.S.; Scheiner, S. Electronic structure and bonding in metal phthalocyanines, Metal=Fe, Co, Ni, Cu, Zn, Mg. J. Chem. Phys. 2001, 114, 9780-9791. (45) Kennedy, B.J.; Murray, K.S.; Zwack, P.R.; Homborg, H.; Kalz, W. Spin states in iron(111) phthalocyanines studied by Mossbauer, magnetic susceptibility, and ESR measurements. Inorg. Chem. 1986, 25, 2539-2545.



(46) Simonato, J.P.; Pecaut, J.; Le Pape, L.; Oddou, J.L.; Jeandey, C.; Shang, M.; Scheidt, W.R.; Wojaczynski, J.; Wołowiec, S.; L. Latos-Grazynski, L.; et al. An integrated approach to the mid-spin state (S=3/2) in six-coordinate iron (III) chiroporphyrins. Inorg. Chem. 2000, 39, 3978-3987. (47) Abdurahman, A.; Renger, T. Density functional studies of iron-porphyrin cation with small ligands X (X: O, CO, NO, O2, N2, H2O, N2O, CO2). J. Phys. Chem. A 2009, 113, 9202–9206. (48) Solano-Peralta, A.; Saucedo-Vázquez, J.P.; Escudero, R.; Hopfl, H.; El-Mkami, H.; Smith, G.M.; Sosa-Torres, M.E. Magnetic and high-frequency EPR studies of an octahedral Fe(III) compound with unusual zero-field splitting parameters. Dalton Trans. 2009, 9, 1668–1674.


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Table 1. Concentration of elements of CuPc and FePc grafted PE determined by XPS. Atomic concentrations of C(1s), O(1s), S (2p), Cu(2p3/2) and Fe(2p3/2) on PE samples: pristine (PE), plasma treated for 120 s (PE/120) and samples treated by plasma for 120 s and subsequently grafted with CuPc and FePc (aMPc, bMPc and cMPc, by different concentrations and grafting times).

Element concentration (at. %) Sample

C(1s)

O(1s)

S(2p)

PE PE/120

100 77.8

22.2

-

-

-

PE/120/aCuPc/1 h PE/120/aCuPc/24 h PE/120/bCuPc/1 h PE/120/bCuPc/24 h PE/120/cCuPc/1 h PE/120/cCuPc/24 h

70.5 71.3 73.8 76.6 71.1 70.9

27.4 26.2 25.0 22.0 28.0 28.5

1.8 2.1 1.2 1.1 0.8 0.4

0.3 0.4 0.1 0.3 0.1 0.2

-

PE/120/aFePc/1 h PE/120/aFePc/24 h PE/120/bFePc/1 h PE/120/bFePc/24 h PE/120/cFePc/1 h PE/120/cFePc/24 h

70.7 71.0 74.8 74.0 69.8 70.5

27.7 26.7 23.1 24.0 26.5 25.6

1.3 2.1 -

-

0.3 0.2 2.1 2.0 3.7 3.9


Cu(2p3/2) Fe(2p3/2)


FIGURE CAPTION Figure 1. Chemical formulas of copper (II) phthalocyanine-3,4′,4ʺ,4‴-tetra-sulfonic acid tetrasodium salt (CuPc, C32H12CuN8O12S4·4 Na) and iron (III) phthalocyanine-4,4′,4′′,4′′′tetrasulfonic acid, compound with oxygen monosodium salt hydrate (FePc, C32H15FeN8O14S4Na·x H2O). Figure 2. Differential UV-Vis spectra of plasma treated (120 s) PE subsequently grafted from water solutions with different concentration of CuPc and FePc (2·10-5, 1·10-5 and 5·10-6 mol·L-1, labelled as aMPc, bMPc and cMPc) for 1 and 24 h. The positions of B and Q band are shown. Figure 3. Deconvolution of Cu (2p3/2) and Fe (2p3/2) peak of PE activated in plasma (120 s) and subsequently grafted with bCuPc (left, PE/120/bCuPc/24 h) and bFePc (right, PE/120/bFePc/24 h) for 24 h. Experimentally obtained results (black line) are compared with a model (red line). Background (blue line) and the position and size of particular components is also shown. Figure 4. Comparison of homogeneity of the Cu and Fe distribution on plasma treated PE (120 s) grafted with bCuPc (left, PE/120/bCuPc/24 h) and aFePc (right, PE/120/aFePc/24 h) for 24 h determined by EDS. Color assignment to each element from top to bottom: C (orange), O (dark cyan), S (purple), Cu (red) and Fe (green). Figure 5. SEM images of plasma treated PE grafted with bCuPc (left, PE/120/bCuPc/24 h) and a

FePc (right, PE/120/aFePc/24 h) for 24 h.

Figure 6. Zeta potential determined on pristine PE (PE), plasma treated PE (PE/120) and PE treated by plasma and grafted with water solutions of different concentrations of CuPc and FePc (2·10-5, 1·10-5 and 5·10-6 mol·L-1, labelled as aMPc, bMPc and cMPc) for 1 and 24 h. Left column is assigned to PE/120/xMPc/1 h and the right (hatched) column belongs to PE/120/xMPc/24 h. Figure 7. ESR spectra of aCuPc, bCuPc and cCuPc samples grafted for 1 or 24 h including the simulation described in the text. Figure 8. Temperature dependence of ESR spectrum of bCuPc grafted for 24 h.


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Figure 9. ESR spectra of aFePc, bFePc and cFePc samples grafted for 1 or 24 h including the simulation described in the text. Figure 10. Temperature dependence of ESR spectrum of aFePc grafted for 24 h.



Figure 1.

Figure 2.


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Figure 3.



Figure 4.


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Figure 5.

Figure 6.



Figure 7.

Figure 8.


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Figure 9.

Figure 10.



TOC Graphic


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The Journal of Physical Chemistry

Chemical formulas of copper (II) phthalocyanine-3,4′,4ʺ,4‴-tetra-sulfonic acid tetrasodium salt (CuPc, C32H12CuN8O12S4·4 Na) and iron (III) phthalocyanine-4,4′,4′′,4′′′-tetrasulfonic acid, compound with oxygen monosodium salt hydrate (FePc, C32H15FeN8O14S4Na·x H2O). 101x40mm (300 x 300 DPI)



Differential UV-Vis spectra of plasma treated (120 s) PE subsequently grafted from water solutions with different concentration of CuPc and FePc (2·10-5, 1·10-5 and 5·10-6 mol·L-1, labelled as aMPc, bMPc and cMPc) for 1 and 24 h. The positions of B and Q band are shown. 101x83mm (300 x 300 DPI)


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Deconvolution of Cu (2p3/2) and Fe (2p3/2) peak of PE activated in plasma (120 s) and subsequently grafted with bCuPc (left, PE/120/bCuPc/24 h) and bFePc (right, PE/120/bFePc/24 h) for 24 h. Experimentally obtained results (black line) are compared with a model (red line). Background (blue line) and the position and size of particular components is also shown. 93x72mm (300 x 300 DPI)



Comparison of homogeneity of the Cu and Fe distribution on plasma treated PE (120 s) grafted with bCuPc (left, PE/120/bCuPc/24 h) and aFePc (right, PE/120/aFePc/24 h) for 24 h determined by EDS. Color assignment to each element from top to bottom: C (orange), O (dark cyan), S (purple), Cu (red) and Fe (green).


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SEM images of plasma treated PE grafted with bCuPc (left, PE/120/bCuPc/24 h) and aFePc (right, PE/120/aFePc/24 h) for 24 h. 127x70mm (300 x 300 DPI)



Zeta potential determined on pristine PE (PE), plasma treated PE (PE/120) and PE treated by plasma and grafted with water solutions of different concentrations of CuPc and FePc (2·10-5, 1·10-5 and 5·10-6 mol·L-1, labelled as aMPc, bMPc and cMPc) for 1 and 24 h. Left column is assigned to PE/120/xMPc/1 h and the right (hatched) column belongs to PE/120/xMPc/24 h. 84x121mm (300 x 300 DPI)


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ESR spectra of aCuPc, bCuPc and cCuPc samples grafted for 1 or 24 h including the simulation described in the text. 169x118mm (300 x 300 DPI)



Temperature dependence of ESR spectrum of bCuPc grafted for 24 h. 169x118mm (300 x 300 DPI)


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ESR spectra of aFePc, bFePc and cFePc samples grafted for 1 or 24 h including the simulation described in the text. 169x118mm (300 x 300 DPI)



Temperature dependence of ESR spectrum of aFePc grafted for 24 h. 169x118mm (300 x 300 DPI)


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TOC graphic


Magnetic and Surface Properties of Metallophthalocyanines (M= Cu, Fe)

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