Two-Dimensional Assembly of Magnetic Binuclear Complexes: a

Aug 11, 2009 - Mono- and binuclear metal-organic compounds bearing long alkyl chains were synthesized and studied at the liquid/graphite interface usi...
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Two-Dimensional Assembly of Magnetic Binuclear Complexes: a Scanning Tunneling Microscopy Study Florian M€ogele,† Donato Fantauzzi,† Ulf Wiedwald,‡ Paul Ziemann,‡ and Bernhard Rieger*,§ †

Institute of Material and Catalysis and ‡Institute of Solid State Physics, University of Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany, and §WACKER-Chair of Macromolecular Chemistry, Technische Universit€ at M€ unchen, Lichtenbergstrasse 4, D-85747 Garching/Munich, Germany Received June 2, 2009. Revised Manuscript Received July 16, 2009 Mono- and binuclear metal-organic compounds bearing long alkyl chains were synthesized and studied at the liquid/ graphite interface using scanning tunneling microscopy. Two different lamellar surface patterns as well as a star like structure were obtained driven by van der Waals interactions of the alkyl chains and weak hydrogen bonds of the phenoxy moieties. In the case of the star like structure solvent molecules (1,2,4-trichlorobenzene) are supposed to play an important role for the stabilization of the created pattern. Magnetic investigation of the bulk material by a superconducting quantum interference device magnetometer revealed magnetic moments up to 1.7 μB (NiCo) and most likely antiferromagnetic coupling between the two metals within a single complex. The presented two-dimensional crystallization of the binuclear complexes may provide an easy access to new designable materials in molecular electronics.

Introduction Two-dimensional aggregation by molecular self-assembly is a very powerful tool known from nature to create functional devices out of smaller building blocks which can, in the laboratory, be created by evaporation and adsorption under UHV conditions,1-3 by applying Langmuir-Blodgett (LB) techniques4 or from a solution.5-7 Especially the latter method is appropriate for organic and metal organic compounds because of the related mild conditions excluding thermal decomposition which might be present in the case of vacuum deposition. In addition, aggregation from a solution is independent of functional groups like thiols or amphiphilic behavior. The resulting assemblies often exhibit properties different from those of the single molecules. Self-assembled monolayers (SAMs) have been intensively investigated over the past years and have found already applications as *To whom correspondence should be addressed. E-mail: [email protected]. Fax: þ49 89 289 13562. Phone: þ49 89 289 13570.

(1) Chiang, S. Science 1996, 272, 1123–1124. (2) Florio, G. M.; Werblowsky, T. L.; M€uller, T.; Berne, B. J.; Flynn, G. W. J. Phys. Chem. B 2005, 109, 4520–4532. (3) Stepanow, S.; Lin, N.; Barth, J. V.; Kern, K. J. Phys. Chem. B 2006, 10, 23472–23477. (4) Dhindsa, A. S.; Bryce, M. R.; Ancelin, H.; Petty, M. C.; Yarwood, J. Langmuir 1990, 6, 1680. (5) Schuurmans, N.; Uji-i, H.; Mamdouh, W.; de Schryver, F. C.; Feringa, B. L.; van Esch, J.; de Feyter, S. J. Am. Chem. Soc. 2004, 126, 13884–13885. (6) Cyr, D. M.; Venkataraman, B.; Flynn, G. W. Chem. Mater. 1996, 8, 1600– 1615. (7) Qiu, X.; Wang, C.; Zeng, Q.; Xu, B.; Yin, S.; Wang, H.; Xu, S.; Bai, C. J. Am. Chem. Soc. 2000, 122, 5550–5556. (8) Ashkenasy, G.; Ivanisevic, A.; Cohen, R.; Felder, C. E.; Cahen, D.; Ellis, A. B.; Shanzer, A. J. Am. Chem. Soc. 2000, 122, 1116–1122. (9) Flink, S.; van Veggel, F. C. J. M.; Reinhoudt, D. N. Adv. Mater. 2000, 12, 1315–1328. (10) Nielson, K. A.; Cho, W.-S.; Lyskawa, J.; Levillain, E.; Lynch, V. M.; Sessler, J. L.; Jeppesen, J. O. J. Am. Chem. Soc. 2006, 128, 2444–2451. (11) Hyun, J.; Chilkoti, A. Macromolecules 2001, 34, 5644–5652. (12) Dai, L.-X. Angew. Chem., Int. Ed. 2004, 43, 5726–5729. (13) Kelly, K. F.; Shon, Y.-S.; Lee, T. R.; Halas, N. J. Phys. Chem. B 1999, 103, 8639–8642. (14) Nakamura, M.; Endo, O.; Ohta, T.; Ito, M.; Yoda, Y. Surf. Sci. 2002, 514, 227–233.

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sensors,8-10 in catalysis11,12 and electrochemistry,13-15 for wetting,16-18 lubrication,19 and solar cells.20 A further promising perspective is to apply SAMs as building blocks for molecular electronics.21 A fundamental aspect of creating functional units by self-assembly is to control the structure and the mutual distances of single molecules within the adlayer which can be achieved by the introduction of functional groups in the basic structure of the molecule.22 An easy to use and common spacer in organic compounds to control the distances of the molecules within the adlayer are long alkyl chains which also support the mutual recognition of the molecules and the stability of the whole pattern. These structural units are very popular for molecules adsorbed on HOPG (highly oriented pyrolytic graphite) because of their high affinity to graphite and high stability of the formed nano pattern. By variation of the length and number of the alkyl chains it is possible to control the distances and even the structure itself after exposing the molecules on a surface.23 Even metal complexes which often exhibit interesting magnetic and electronic properties can be highly ordered on surfaces and can be easily designed by standard synthesis methodologies of their organic ligands. In prospect, they allow access to new materials and building blocks for molecular electronics and may be used as magnetic switches or data storage devices. Especially binuclear complexes provide the possibility to fine-tune the magnetic properties by control of (15) Yoshimoto, S.; Higa, N.; Itaya, K. J. Am. Chem. Soc. 2004, 126, 8540–8545. (16) Bain, C. D.; Whitesides, G. M. Angew. Chem., Int. Ed. Engl. 1989, 28, 506– 512. (17) Chaudhury, M. K.; Whitesides, G. M. Science 1992, 255, 1230–1232. (18) Jiang, Y.; Wan, P.; Smet, M.; Wang, Z.; Xi, Z. Adv. Mater. 2008, 20, 1972– 1977. (19) Zhang, Q.; Archer, L. A. J. Phys. Chem. B 2003, 107, 13123–13132. (20) Khodabakhsh, S.; Sanderson, B. M.; Nelson, J.; Jones, T. S. Adv. Mater. 2006, 16, 95–100. (21) Carroll, R. L.; Gorman, C. B. Angew. Chem., Int. Ed. 2002, 41, 4378–4400. (22) Kikkawa, Y.; Koyama, E.; Tsuzuki, S.; Fujiwara, K.; Miyake, K.; Tokuhisa, H.; Kanesato, M. Langmuir 2006, 22, 6910–6914. (23) Zell, P.; M€ogele, F.; Ziener, U.; Rieger, B. Chem.;Eur. J. 2006, 12, 3847– 3857.

Published on Web 08/11/2009

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Scheme 1. Synthesis of the Binuclear Complexes bin1-bin14 Derived from 2,4-Dihydroxyacetophenone As a Starting Material for the Ligandsa

a ac1: R1 = C16H33, ac2: R1 = C12H25, dik1: R1 = C16H33, dik2: R1 = C12H25, en1: R1 = C16H33, en2: R1 = C12H25, M1/M2 = metal centers (see Table 1).

the intramolecular structure. Moreover, self-assembled monolayers of these molecules also offer the possibility to tailor the intramolecular electronic interactions. Besides application in molecular electronics based on their magnetic properties, metal complexes contribute as well to the development of new screens24 and even in catalysis.25 In this communication we present a study of the self-assembly of a ligand system bearing two different coordination sites which provide electronic interactions between the two metal centers within one molecule. Although the synthesis of the moiety of the molecules with the coordination sites is already known in literature,26,27 the introduction of long alkyl chains in the ligand system required a modification of the described preparation. The monolayers were created and measured at the liquid/solid interface using scanning tunneling microscopy (STM) which provides submolecular resolution of the formed adlayers. The investigation of the magnetic properties of the binuclear complexes in bulk is also provided to get an insight of the magnetic properties of the single molecule in bulk without any further aggregation as a first step of the further investigation with regard to the property of the monolayer.

Results and Discussion Synthesis of Mono- And Binuclear Metal Complexes. Prior to the structural and magnetic characterization by STM and Superconducting Quantum Interference Detection (SQUID) measurements, a ligand system derived from 2,4-dihydroxyacetophenone with two different coordination sites was synthesized and characterized together with the corresponding mono- and binuclear metal complexes. Scheme 1 shows the principal synthetic pathway to the desired complexes. In a first step 4-alkylated 2,4-dihydroxyacetophenones (24) Kou, H.-Z.; Li, D.-Z.; Zhou, B.-C.; Wang, R.-J.; Li, Y. Inorg. Chem. 2002, 41, 4756–4762. (25) Luinstra, G. A.; Haas, G. R.; Molnar, F.; Bernhart, V.; Eberhardt, R.; Rieger, B. Chem.;Eur. J. 2005, 11, 6298–6314. (26) Fenton, D. E.; Gayda, S. E.; Casellato, U.; Vigato, P. A.; Vidali, M. Inorg. Chim. Acta 1978, 27, 9–14. (27) Graziani, R.; Vidali, M.; Rizzardi, G.; Casellato, U.; Vigato, P. A. Inorg. Chim. Acta 1979, 36, 145–150.

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Table 1. Synthesized Mono- And Binuclear Complexes with Different Chain Length and Metal Centers compound mononuclear complexes

binuclear complexes

metal-1 mo1 mo2 mo3 mo4 bin1 bin2 bin3 bin4 bin5 bin6 bin7 bin8 bin9 bin10 bin11

metal-2

II

Ni NiII CuII PdII NiII NiII NiII NiII NiII NiII NiII NiII NiII NiII NiII

VOII CuII VOII MnII FeII CoII NiII CuII ZnII PdII PtII

R1 C16H33 C12H25 C12H25 C12H25 C16H33 C16H33 C12H25 C12H25 C12H25 C12H25 C12H25 C12H25 C12H25 C12H25 C12H25

ac1 and ac2 were prepared by etherification of the commercially available 2,4-dihydoxyacetophenone at 4-position with 1-bromalkanes in boiling acetone in presence of KHCO3 and a catalytical amount of KI according to a previously reported procedure in literature.28 To obtain an additional coordination site a second keto function was introduced by a claisen condensation of ac1 and ac2 with a 5-fold excess of ethyl acetate in dry toluene in presence of an 8-fold excess of NaH at 70 °C. In the NMR spectra the keto as well as the enolform of dik1 and dik2 can be clearly distinguished whereas the intensity of the peaks of the two sets of signals depends on the amount of protonic solvents in the deutero chloroform which was used for NMR investigations. Finally, two ligand molecules were bridged by the reaction of the butane-1,3-dione (dik1 or dik2) with 0.5 equiv of 1,2-ethylendiamine in a mixture of methanol and chloroform at room temperature which led to en1 and en2, whereas the resulting signals in the proton NMR-spectra and their integrals reveal the formation of enamins. The mononuclear compounds were synthesized from en1 or en2 in a boiling (28) Lai, C. K.; Chen, F.-G.; Ku, Y.-J.; Tsai, C.-H.; Lin, R. J. Chem. Soc., Dalton Trans. 1997, 4683–4687.

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solution of the ligand in a mixture of methanol and chloroform under the addition of an equimolar amount of a metal acetate precursor.26,27,29,30 A characteristic color change took place within seconds. It is noteworthy to say that it is the N2O2-cage where the first metal is coordinated which is indicated by the NMR- and IR-spectra for the nickel and palladium complex and the IR-spectra of the paramagnetic copper compound. In the last step the binuclear compounds were synthesized by the reaction of the mononuclear complex mo1 or mo3 and a suitable metal salt precursor in the presence of a 6-fold excess of LiOH in boiling ethanol. The high excess of LiOH was necessary to dissolve the mononuclear complex completely. In the IR-spectra of all mononuclear complexes show two modes at about 1624 cm-1 and 1595 cm-1 which can be assigned to CdO and CdC vibrations or rather their combination while in the spectra of all binuclear complexes just one signal appears at about 1604 cm-1. The mode of the phenolic C-O vibration is also shifted to higher wavelengths (about 1303 cm-1 for mononuclear complexes and about 1311 cm-1 for all binuclear complexes). These results agree with the findings in previous reports in literature.29 The elemental analysis of the complexes reveal that most of the obtained binuclear complexes include 2 equiv of LiOH per molecule whereas the two hydroxides are assumed to complex the second metal in an octahedral manner. This is supported by the excess of employed LiOH and by the preferred octahedral surrounding of the employed metals. Even the PdII-NiII (bin10) and the PtII-NiII (bin11) complex were obtained bearing two units of LiOH although PdII and PtII form exclusively planar quadratic complexes. Exchange of the coordination place of nickel and palladium or platinum is supposed because of the low affinity of palladium and platinum to oxygen and additionally coordination of NiII by two OH in the O2O2-cage. STM Investigations of Self-Assembled Monolayers. Prior to the STM investigations the compounds were dissolved in 1,2,4trichlorobenzene (TCB) and exposed as a droplet on freshly cleaved highly oriented pyrolytic graphite (HOPG). The STM images were obtained in the constant current mode under ambient conditions with the tip immersed in the supernatant solution. Lamellar Pattern Type I. All measured mononuclear complexes crystallized in a lamellar pattern with big domains which are only limited by graphite steps. The distances of the molecules in the obtained structures depend on the alkyl chain length and the metal center itself. The influence of the length of the alkyl chain can be observed from the STM images of mo1 and mo2 at the liquid/solid interface as shown in Figure 1. The characteristic feature in this lamellar structure (L1-pattern) is that molecules of neighbored lamellae and therefore the lamellae itself are twisted by an angle of 180° to each other. Because the molecules adsorb in such a way that they have an intramolecular mirror plane which coincides with the lamella main axis and the special arrangement within the adlayer, the domains are non-chiral. The periodicity in the 2D formation of the OC16 substituted NiII complex is dramatically changed when mo2, the same compound with four less methylene groups, is adsorbed on the surface (51 A˚ ( 1 A˚ for mo1 and 31 A˚ ( 1 A˚ for mo2). The distance between the lamellae is smaller (15.8 A˚ ( 0.2 A˚) but less than expected for a C12 chain with exactly the same structure as mo1 (27 A˚ ( 1 A˚). The reason for this is the different bending of the alkyl chains with respect to the lamella main axis which is significantly larger in the structure (29) Chisari, A.; Musumeci, A.; Vidali, M.; Seminara, A. Inorg. Chim. Acta 1984, 81, L19–L21. (30) Shama, S. A.; Omara, H. Spectrosc. Lett. 2001, 34, 49–56.

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of mo1 (see Table 2). The smaller angle of the alkyl chains for mo2 results in larger distances between adjacent molecules (17.8 A˚ ( 0.2 A˚) within the lamellae as compared to mo1 (10.1 A˚ ( 0.2 A˚). In contrast to mo2, the alkyl chains in the pattern of mo1 are densely packed (approximately 4.5 A˚) while in the adlayer of mo2 only every second alkyl chain reaches this distance to the following chain. The high resolution images of the present complexes and the obtained measurements allow us to set up a structural model, in which the alkyl chains of adjacent lamellae interdigitate. The proximity of the molecules within the adlayer of mo1 suggests weak intermolecular interactions between the hydrogens of the terminal methyl group near the ethylene bridge and the alkoxy-O of a neighbored complex. By applying typical distances of the atoms in molecules we can evaluate this bonding distance as 2.9 A˚ (Figure 1 E), which is within the reasonable range for this interaction (1.6 A˚-3.2 A˚).31-33 The shortening of the alkyl chain length from C16 to C12 finally results in loss of these weak CH 3 3 3 O hydrogen bonds because of greater distances between corresponding atoms and hindering by the alkyl chains. This small reorganization in mo2 in contrast to mo1 leads to weak bonds between hydrogens of the terminal methyl groups of the alkyl chains and an alkoxy-O (3.0 A˚) of an appropiate neighboring complex which support the created pattern. It is noteworthy to say that the packing density of the pattern of mo1 (0.37 molecules/nm2 ( 0.2) despite the longer chain is higher than that of the surface structure of mo2 (0.36 molecules/nm2 ( 0.2) with the shorter chain. The corresponding OC12 substituted CuII- and PdII-complexes crystallized in the same structure as mo2 but with a decreased interlamellar distance of adjacent molecules and increased periodicity in accordance with the larger ion radius. A value of 0.32 molecules/nm2 ((0.2) was determined for the resulting packing densities of mo3 and mo4. The smallest angle with respect to the lamella main axis was obtained for mo3 while the corresponding angle in the monolayer of mo6 is almost the same as in the structure of mo2 (34° ( 2° for mo3 and 36° ( 2° for mo4). Table 2 shows the results as obtained from the STM images. All investigated OC12 substituted binuclear compounds except the FeII-NiII (bin5) and the CoII-NiII crystallized in the L1-pattern like the corresponding mononuclear NiII-Precursor mo1 or mo2, whereas the resulting adlayers can be clearly distinguished from the mononuclear complexes because of different periodicities and distances between adjacent molecules within the lamellae. The visualized domains though being large are not limited by substrate steps. In the pattern of binuclear complexes with a 3d element at the second coordination site of the ligand, the distance between adjacent molecules within the lamellae (16.6 A˚-17.0 A˚ ( 0.2 A˚) and the periodicities differ just slightly (33 A˚-34 A˚ ( 1 A˚). The largest interlamellar distance of adjacent molecules of 18.8 A˚ ((0.2 A˚) was obtained for the NiIIPdII complex with the smallest measured periodicity (29.5 A˚ ( 0.2 A˚). It is noteworthy to say that the LiOH adducts of some investigated complexes aggregate in the same way as the corresponding binuclear complexes without additional LiOH. Therefore, it is supposed that the LiOH do not influence the aggregation and the resulting pattern. Nevertheless the obtained resolution of the obtained STM-images was less than that for the complexes without additional LiOH. Lamellar Pattern Type II. In contrast to that, for the corresponding binuclear complexes bin1 and bin2 again a lamellar (31) Huang, W.; Zhu, H.-B.; Gou, S.-H. Coord. Chem. Rev. 2006, 250, 414–423. (32) de Almeida, E. T.; Mauro, A. E.; Santana, A. M.; Ananias, S. R.; Netto, A. V. G.; Ferreira, J. G.; Santos, R. H. A. Inorg. Chem. Commun. 2007, 10, 1394–1398. (33) Lewinski, J.; Zachara, J.; Justyniak, I.; Dranka, M. Coord. Chem. Rev. 2005, 249, 1185–1199.

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Figure 1. (A) STM image of OC16 substituted mononuclear NiII-complex mo1 at the TCB/HOPG interface, image area 20.0  20.0 nm2, Uset = -140 mV, Iset = 6.6 pA and (B) structure model, unit cell dimension: a = 10.1 A˚, b = 52 A˚, R = 94°; (C) STM image of mo3 at HOPG, image area 20.0  20.0 nm2, Uset = -745 mV, Iset = 13.0 pA; (D) structure model for the surface structure of mo3 and unit cell dimensions: a = 17.8 A˚, b = 31 A˚, R = 85°; (E) suggested intramolecular CdO 3 3 3 H and intermolecular CAliphatH 3 3 3 OAlkoxy hydrogen bonding for additional stabilization of the adlayer of mo1.

structure (L2-pattern) is observed, which, however, differs in detail. In the case of bin2 even a second star like modification was observed. Figure 2 shows both surface modifications of bin2 at the TCB/HOPG interface and corresponding structural models. In contrast to the precursor mo1, the periodicity of the lamellar modification is much smaller (51 A˚ ( 1 A˚ for mo1 and 34 A˚ ( 1 A˚ for bin2) while adjacent molecules within a lamella are 22.5 A˚ ((0.2 A˚) apart. The alkyl chains are densely packed and only interdigitate with chains of one neighbored lamella. The created surface structure suggests weak Caliphat-H 3 3 3 Ophenolat hydrogen bonding (approximately 3.1 A˚-3.7 A˚) which stabilizes the structure under van der Waals interactions of the alkyl chains. Star Like Pattern. The second modification of bin2 consists of several homochiral domains which are built up by hexagonal ordered aggregates which are formed by six individual complexes. The height profile across an aggregate reveals three local maxima whereas the exterior signals can be assigned to aromats of two opposite molecules within an aggregate while the center signal is Langmuir 2009, 25(23), 13606–13613

assumed to be a result of a coadsorbed solvent molecule (TCB) which stabilizes the structure by Caryl-H 3 3 3 Cl hydrogen bonding. Magnetic Behavior of the Binuclear Complexes. Dried powders of binuclear complexes bin3-bin8 were examined by means of SQUID magnetometry to look for trends of the magnetization along the Ni-3d-metal series. Figure 3 presents the experimental results at T=2 K. The largest magnetic moment per molecule μm =1.73 μB is observed for bin6 (NiCo) while for lighter and heavier Ni-3d molecules the magnetization decreases reaching 0.27 μB for bin1 (NiV) and 0.63 μB for bin8 (NiCu). With the exception of bin4 all other magnetization curves saturate in an external field of 5.5 T at 2K. The observed data cannot be simulated by Brillouin functions indicating the failure of any model assuming independent magnetic moments. Rather, intramolecular and, possibly, intermolecular coupling has to be taken into account. Some hints as to the sign of the coupling mechanism between the two magnetic spins within a molecule, that is, ferromagnetic (FM) or antiferromagnetic (AFM) coupling, DOI: 10.1021/la9019712

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Table 2. Distances of the Mono- Binuclear Complexes within the Adlayer, Unit Cell Dimensions, and Density of the Structure Depending on Metal Center and Alkyl Chain Length

mo1 (NiC16) mo2 (NiC12) mo3 (CuC12) mo4 (PdC12) bin1 (NiVOC16) bin2 (NiCuC16) bin2 (NiCuC16) bin3 (NiVOC12) bin4 (NiMnC12) bin5 (NiFeC12) bin6 (NiCoC12) bin8 (NiCuC12) bin10 (NiPdC12)

d (M-M) [(0.2 A˚]

periodicity [(1 A˚]

pattern

10.1 17.8 17.0 16.5 19.7 22.5 52 12.1 21.8 16.9 35 16.6 18.8

51 31 35 38 27.2 34 97 34 28.1 33 75 34 29.5

L1 L1 L1 L1 L1 L2 S L1 L1 L2 S L1 L1

unit cell dimensions

a [(0.2 A˚]

b [(1 A˚]

R [(2°]

molecules per area [1/nm2 ( 0.02]

mo1 (NiC16) mo2 (NiC12) mo3 (CuC12) mo4 (PdC12) bin1 (NiVOC16) bin2 (NiCuC16) bin2 (NiCuC16) bin3 (NiVOC12) bin4 (NiMnC12) bin5 (NiFeC12) bin6 (NiCoC12) bin8 (NiCuC12) bin10 (NiPdC12)

10.1 17.8 17.0 16.5 19.7 22.5 54 12.1 21.8 16.9 35 16.6 18.8

52 31 37 38 29.3 34 52 36.4 31 36 40 35 32

94 81 94 85 74 76 51 73 91 84 71 94 77

0.37 0.36 0.32 0.32 0.36 0.27 (L2-pattern) 0.27 (S-pattern) 0.47 0.30 0.33 0.45 0.35 0.34

Figure 2. STM visualization of both surface modifications obtained from bin2; (A) lamellar modification, image area 15.0  15.0 nm2, Uset = -998 mV, Iset = 23.1 pA; (B) structure model for the lamellar pattern, unit cell dimension: a = 22.5 A˚, b = 34 A˚, R = 76°; (C) star like modification, image area 20.2  20.2 nm2, Uset = -157 mV, Iset = 19.5 pA; (D) section view along the black line in C; (E) structure model of the star like modification, unit cell dimension: a = 54 A˚, b = 52 A˚, R = 51°. 13610 DOI: 10.1021/la9019712

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By arrangement of these binuclear compounds in a monolayer their magnetic moments which have been measured are also arranged in a well-defined manner with defined distances. Within the highly ordered monolayer the magnetic moment of the single molecule should be able to couple over a vast area which should result in a higher magnetic moment. This may exist at temperatures even higher than 2 K, and possibly the resulting moments could be addressed by an external magnetic field.

Figure 3. Magnetization of binuclear complexes bin3-bin8 as a function of external field at T = 2 K (upper panel). The lower panel shows magnetic moment per molecule at B = 5.5 T and T = 2 K. Except bin4 the magnetic moment is saturated.

can be extracted from the experiments by applying a spin-only model. In such a crude model, 3d orbitals are filled up according to Hund’s rules with exclusively spin-moments being considered while orbital magnetic moments are assumed to be completely quenched. Moreover, any charge transfer from or into the 3d states is neglected. For FM coupling one expects 3-7 μB per molecule with a maximum for the Ni-Mn molecule while for AFM coupling the effective magnetic moment per molecule lies between 0 and 3 μB. The experimental results (0.27-1.73 μB) clearly point to an AFM coupling. Interestingly, the bin7 (NiNi) binuclear complex shows a non-vanishing magnetic moment as opposed to the expectation for identical magnetic moments at both Ni sites and AFM alignment at T=2K. Thus, the non-zero effective moment observed for the Ni-Ni complex clearly indicates the influence of the local environment, which indeed is different for the two Ni atoms. As a consequence, the above rough estimate of the moments has to be substituted by more detailed modeling like employing ligand field theory including charge transfer and orbital magnetism.34 From an experimental point of view it is obviously desirable to apply an element-specific technique, such as X-ray magnetic circular dichroism,35 to achieve a direct proof of AFM coupling in or close to the magnetic ground state. Such experiments are under way. (34) Kahn, O. Molecular Magnetism, 1st ed.; John Wiley & Sons: Singapore, 1993; Chapter 1. (35) Khanra, S.; Kuepper, K.; Weyherm€uller, T.; Prinz, M.; Raekers, M.; Voget, S.; Postnikov, A. V.; de Groot, F. M. F.; George, S. J.; Coldea, M.; Neumann, M.; Chaudhuri, P. Inorg. Chem. 2008, 47, 4605.

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Conclusion In summary, we have shown the preparation and 2D crystallization of binuclear metal organic complexes which may allow access to novel materials for molecular electronics. A series of Ni-3d binuclear complexes were synthesized from a previously designed ligand system containing two close different coordination sites. STM investigations at the liquid/solid interface of the molecules disclosed highly ordered close packed monolayers. The creation of these nanopatterns are mainly driven by van der Waals interacions of the long alkyl chains of adjacent molcules of neighboring lamellae and by weak hydrogen bonding. While the OC12 as well as the OC16 substituted mononuclear NiII-complexes crystallized in the same lamellar structure type (L1-pattern), the investigated OC16 substituted binuclear complexes formed a second lamellar modification and/or even a star like structure. The last mentioned pattern is assumed as a coadsorbate of the complex and solvent molecule. SQUID magnetometry on powders revealed a non-vanishing magnetic moment for all Ni-3d element binuclear complexes. The experimental results suggest antiferromagnetic coupling at T=2 K. The 2D crystallization of the presented binuclear metal complexes may be a new approach to get fast and easy access to new designable materials in molecular electronics. Experimental Section Materials and Methods. Sodium hydride (60% suspension in paraffin oil), 2,4-dihydroxyacetophenone, 1-bromo hexadecane, 1-bromo dodecane, 1,2-ethylendiamine, absolute solvents, and the metal salts were purchased from different suppliers and used without further purification. Toluene was distilled over sodium and stored under argon. Standard NMR measurements were recorded on Avance 400 from Bruker. FTIR measurements were carried out on Bruker IFS FT-IR with a resolution of 2 cm-1 and the elemental analysis were recorded on Vario EL from Vario. A low-current scanning tunneling mmicroscope (RHK Technology Inc., Troy, MI, U.S.A.; UHV 300, IVP 300, SPM 1000) with negative sample bias was used. STM tips (Pt/Ir 80:20, Advent, Cambridge) were mechanically sharpened. HOPG (PLANO) was used as a substrate as well as for internal calibration. Prior to the STM measurements the compounds were solved in 1,2,4-trichlorobenzene (2-3 mg/mL). The STM images were obtained in the constant current mode under ambient conditions with the tip immersed in the supernatant solution. A droplet was exposed on HOPG, and the monolayers formed within seconds without any further visible dynamic of the structure during the whole measurement time of several hours. Lamellar structures were preferred because of the long alkyl chains which are responsible for the mutual recognition of the molecules and therefore under intermolecular hydrogen bonding interactions, the main driving force in the formation of the 2D crystal. In the STM images the aromatic components of the molecules appear as bright parts because of the higher conductivity of the vertical pz-orbital of the π-system while the alkyl chains are resolved in the darker areas. Even the metal center, at least the one in the N2O2-cage, is represented as a spot which is even brighter than the aromatic parts because of suitable conductive orbitals. Together with the spots of the aromats, triangles are created whose measurements DOI: 10.1021/la9019712

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Article coincide with the obtained distances in the structural model. In the case of binuclear complexes, the second metal in the O2O2-cage can not be distinguished from the aromatic parts in the STM image. It is supposed that the coordination site does not support higher conductivity in that place. The measurements were repeated several times with different tips to prove the reproducibility of the structures. STM images were processed with WSxM.36 The magnetic properties were measured with a Quantum Design MPMS superconducting quantum interference device (SQUID) magnetometer. Dried powder (typically 5 mg) of binuclear complexes was enclosed in gelatin capsules, and the total magnetic moment of the sample was determined in external fields up to μ0H= 5.5 T at a temperature of T = 2 K. The magnetic signal of the container as obtained from a reference experiment on empty capsules is subtracted. The magnetic moment per molecule is calculated from the net mass of the powder and its molecular weight. The error bar is on the order of 2-5%, mainly because of weighing of the powders and variations of capsules’ mass.

Synthesis of Ligands. 4-Hexadecyl-2-hydroxyacetophenon (ac1). 2,4-Dihydroxyacetophenone (4.18 g, 27.4 mmol), 1-bromhexadecane (8.34 mL, 27.3 mmol), potassium carbonate (3.77 g, 27.3 mmol), and a catalytical amount of KI were suspended in abs. acetone (200 mL) and boiled 24 h under reflux. Subsequently the mixture was allowed to cool down to room temperature and was filtered. The filtrate was poured into a solution of 2 M hydrochloric acid and was extracted with diethylether (3  50 mL). The combined organic phases were washed subsequently with a saturated NaHCO3-solution and water. After drying over Na2SO4 and removal of the solvents under reduced pressure, the residue was recrystalized from ethanol to yield a white crystalline solid. Yield: 4.70 g (12.5 mmol, 46%). 1H NMR (CDCl3): δ 0.86 (t, J=7.0 Hz, 3H), 1.23-1.43 (m, 26H), 1.76 (m, 2H), 2.53 (s, 3H), 3.96 (t, J=7.1 Hz, 2H), 6.37 (d, J=2.5 Hz, 1H), 6.40 (dd, J=8.8 Hz, J=2.5 Hz, 1H), 7.59 (d, J= 8.8 Hz, 1H), 12.73 (s, 1H). 13C NMR (CDCl3): δ 14.09, 22.67, 25.92, 26.13, 28.94-29.68, 31.91, 68.41, 101.29, 108.00, 113.74, 132.20, 165.27, 165.76, 202.43. IR (KBr): 2957, 2917, 2849, 1646, 1615, 1471, 1366, 1253, 838, 797 cm-1. Anal. Calcd for C24H40O3: C, 76.55; H, 10.71. Found: C, 71.09; H, 10.66. 4-Dodecyl-2-hydroxyacetophenon (ac2). The synthesis of ac2 was performed analogously to the methodology described for ac1 by the reaction of 2,4-dihydroxyacetophenone (11.27 g, 74.07 mmol), 1-bromdodecane (18.46 g, 74.07 mmol), and KHCO3 (7.49 g, 74.07 mmol) in abs. acetone (250 mL) within 24 h under reflux. Yield: 4.75 g (14.82 mmol, 20%). 1H NMR (CDCl3): δ 0.85 (t, J=6.9 Hz, 3H), 1.24-1.47 (m, 26H), 1.75 (m, 2H), 2.51 (s, 3H), 3.96 (t, J=6.6 Hz, 2H), 6.36 (d, J=2.3 Hz, 1H), 6.40 (dd, J=8.8 Hz, J=2.5 Hz, 1 H), 7.58 (d, J=8.8 Hz, 1H), 12.70 (s, 1H). 13C NMR (CDCl3): δ 14.04, 22.63, 25.89, 26.06, 28.9129.60, 31.8, 68.38, 101.28, 107.98, 113.70, 132.20, 165.22, 165.75, 202.45. IR (KBr): 2957, 2919, 2851, 1641, 1615, 1472, 1366, 1253, 836, 797 cm-1. Anal. Calcd for C20H32O3: C, 74.96; H, 10.06. Found: C, 72.99; H, 9.75. 1-(4-Hexadecyl-2-hydroxyphenyl)butan-1,3-dion (dik1). A solution of 4-hexadecyloxy-2-hydroxyacetophenone (6.91 g, 18.3 mmol) and a 6.5-fold excess of ethyl acetate (10.60 g, 119.3 mmol) in dry toluolene (20 mL) was added slowly to a suspension of an 8-fold excess of NaH (5.87 g, 146.8 mmol) in dry toluene (250 mL) at room temperature under argon. Afterward the mixture was stepwise heated up to 70 °C and finally stirred at this temperature for 24 h. During this time a tough voluminous yellow solid was formed. The mixture was then cooled to room temperature and under vigorously stirring water, and subsequently a solution of 2 M hydrochloric acid was added until a pH < 6 was obtained. The mixture was extracted with diethylether, and the combined organic phases were washed with a saturated solution of NaHCO3 and water and were dried over Na2SO4. The solvent was removed, (36) Horcas, I.; Fernandez, R.; Gomez-Rodriguez, J. M.; Colchero, J.; GomezHerrero, J.; Baro, A. M. Rev. Sci. Instrum. 2007, 78, 013705.

13612 DOI: 10.1021/la9019712

M€ ogele et al. and the remaining solid recrystallized from ethanol to obtain a slightly yellow solid. Yield: 3.45 g (8.24 mmol, 45%). 1H NMR (CDCl3): δ=0.86 (t, J=6.8 Hz, 3H), 1.24-1.42 (m, 26H), 1.76 (m, 2H), 2.09 (s, 2H), 2.27 (s, 1H), 3.96 (t, J=6.4 Hz, 2H), 3.98 (s, 0.68H), 6.01 (s, 0.66H), 6.39 (d, J=3.0 Hz, 1H), 6.42 (dd, J1 = 9.6 Hz, J2=2.5 Hz, 1H), 7.51 (m, 1H), 12.40 (s, 0.34H), 12.49 (s, 0.66H), 14.79 (s, 0.66H). 13C NMR (CDCl3): δ 14.09, 22.53, 22.68, 25.90, 28.90-29.68, 30.38, 31.92, 54.48, 68.35, 94.89, 101.45, 101.75, 108.18, 108.66, 111.81, 113.35, 130.02, 132.34, 165.32, 165.42, 165.85, 166.42, 180.98, 194.28, 197.20, 201.64; IR (KBr): 3220, 2954, 2919, 2851, 1646, 1604, 1577, 1252, 782, 650, 543 cm-1. Anal. Calcd for C26H42O4: C, 74.60; H, 10.11. Found: C, 74.17; H, 10.20. 1-(4-Dodecyl-2-hydroxyphenyl)butan-1,3-dion (dik2). According to the procedure described for dik1 the OC12 substituted diketone dik2 was prepared by the addition of ac2 (5.31 g, 16.57 mmol) and ethyl acetate (9.50 g, 107.70 mmol) in toluene (20 mL) to a suspension of NaH (5.04 g, 126.00 mmol) in dry toluene (150 mL) under argon. Yield: 1.21 g (3.35 mmol, 20%). 1H NMR (CDCl3): δ 0.86 (t, J=6.9 Hz, 3H), 1.25-1.43 (m, 18H), 1.76 (m, 2H), 2.08 (s, 2H), 2.27 (s, 1H), 3.95 (t, J=6.3 Hz, 2H), 3.98 (s, 0.68H), 6.01 (s, 0.66H), 6.38 (d, J=3.0 Hz, 1H), 6.42 (dd, J1=9.6 Hz, J2=2.5 Hz, 1H), 7.51 (m, 1H), 12.39 (s, 0.34H), 12.48 (s, 0.66H), 14.78 (s, 0.66H). 13C NMR (CDCl3): δ 14.07, 22.52, 22.66, 25.89, 28.45-29.63, 30.37, 31.90, 54.46, 68.41, 94.89, 101.46, 101.75, 108.16, 108.64, 111.82, 113.35, 130.03, 132.34, 165.31, 165.42, 165.85, 166.42, 180.98, 194.28, 197.21, 201.63; IR (KBr): 2954, 2919, 2853, 1627, 1580, 1249, 800, 650, 545 cm-1. Anal. Calcd for C22H34O4: C, 72.89; H, 9.45. Found: C, 72.64; H, 9.46.

N,N-Bis[(4-hexadecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diamin (en1). 1-(4-Hexadecyloxy-2-hydroxyphenyl)butan-1,3-dion (dik1) (819.34 mg, 1.96 mmol) was suspended in methanol (8 mL) and dissolved completely by dropwise addition of CHCl3 (10 mL) at room temperature. The resulting mixture was combined with a solution of ethylendiamine (8.81 mg, 0.98 mmol) in methanol (2 mL) and was stirred for 24 h at room temperature. A yellow solid participated which could be increased by reduction of the solvent under reduced pressure. After recrystallization from EtOH/CHCl3 (1:1) a yellow voluminous solid was obtained. Yield: 253.21 mg (0.29 mmol, 32%). 1H NMR (CDCl3): δ 0.86 (t, J=6.9 Hz, 6H), 1.23-1.41 (m, 52H), 1.73 (m, 4H), 2.06 (s, 6H), 3.55 (m, 4H), 3.93 (t, J=6.6 Hz, 4H), 5.57 (s, 2H), 6.33 (dd, J1=8.6 Hz, J2=2.5 Hz, 2H), 6.35 (d, J=2.3 Hz, 2H), 7.49 (d, J= 8.8 Hz, 2H), 10.87 (s, 2H), 13.77 (s, 2H). 13C NMR (CDCl3): δ 14.10, 19.68, 22.69, 25.99, 29.09-31.92, 43.96, 68.10, 91.23, 101.97, 106.97, 113.57, 129.07, 163.72, 164.42, 164.65, 190.43. IR (KBr): 2921, 2850, 1598, 1552, 1344, 1249, 839, 775, 718 cm-1. Anal. Calcd for C54H88N2O6: C, 75.13; H, 10.23; N, 3.31. Found: C, 75.22; H, 10.34; N, 3.54.

N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diamin (en2). The preparation was performed according to the methodology as described for en1 with a solution of dik2 (502.19 mg, 1.39 mmol) in methanol/CHCl3 (5 mL/8 mL) and a solution of ethylendiamin (41.63 mg, 0.69 mmol) in methanol (2 mL). Yield: 182.21 mg (0.24 mmol, 35%). 1H NMR (CDCl3): δ 0.86 (t, J=6.8 Hz, 6H), 1.15-1.45 (m, 36H), 1.73 (m, 4H), 2.06 (s, 6H), 3.55 (m, 4H), 3.93 (t, J=6.6 Hz, 4H), 5.57 (s, 2H), 6.38 (dd, J1=5.1 Hz, J2=2.5 Hz, 2H), 6.34 (d, J=2.5 Hz, 2H), 7.49 (d, J= 8.9 Hz, 2H), 10.87 (s, 2H), 13.77 (s, 2H). 13C NMR (CDCl3) δ 14.11, 20.00, 22.70, 26.01, 29.11-31.93, 41.95, 46.44, 68.07, 90.47, 101.73, 106.81, 113.73, 128.85, 163.46, 164.59, 164.67, 189.92. IR (KBr): 2922, 2851, 1601, 1554, 1355, 1252, 833, 773, 716 cm-1. Anal. Calcd for C46H72N2O6: C, 73.76; H, 9.69; N, 3.74. Found: C, 73.58; H, 9.84; N, 3.62.

Synthesis of Mono- and Binuclear Complexes. [N,N-Bis[(4-hexadecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2diaminato]nickel(II) (mo1). To a suspension of en1 (497.34 mg, 0.52 mmol) in boiling methanol (20 mL) was added chloroform Langmuir 2009, 25(23), 13606–13613

M€ ogele et al. until complete dissolution. Afterward a solution of nickel(II) acetate tetrahydrate (289.58 mg, 1.16 mmol) in methanol (20 mL) was added where the color changed rapidly almost to black. After 5 h stirring under reflux the reaction was cooled to room temperature. The participate was filtered and washed with ethanol. Yield: 272.08 mg (0.30 mmol, 57%). 1HNMR (CDCl3): δ 0.86 (t, J = 6.9 Hz, 6H), 1.24-1.39 (m, 52H), 1.72 (m, 4H), 1.99 (s, 6H), 3.06 (m, 4H), 3.89 (t, J=6.6 Hz, 4H), 5.49 (s, 2H), 6.27 (dd, J1=8.8 Hz, J2= 2.5 Hz, 2H), 6.40 (d, J=2.5 Hz, 2H), 7.29 (d, J=9.1 Hz, 2H), 10.69 (s, 2H). 13C NMR (CDCl3): δ 14.10, 21.99, 22.67, 26.00, 29.1131.92, 53.32, 68.00, 97.00, 102.76, 107.20, 112.50, 127.68, 160.99, 162.26, 165.39, 172.08. IR (KBr): 2921, 2850, 1625, 1594, 1503, 1361, 1246, 1187, 768 cm-1. Anal. Calcd for C54H86N2NiO6: C, 70.42; H, 9.37; N, 3.10. Found: C, 68.84; H, 9.22; N 3.26.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]nickel(II) (mo2). The synthesis of mo2 was performed analogously to the methodology described for mo1 by the reaction of en3 (2.00 g, 2.67 mmol) in methanol/chloroform (60 mL/45 mL) and nickel(II) acetate tetrahydrate (1.31 g, 5.23 mmol) in methanol (5 mL). Yield: 1.54 g (1.92 mmol, 72%). 1H NMR (CDCl3): δ 0.86 (t, J=6.8 Hz, 6H), 1.21-1.42 (m, 36H), 1.71 (m, 4H), 1.94 (s, 6H), 3.05 (m, 4H), 3.93 (t, J=6.5 Hz, 4H), 5.55 (s, 2H), 6.27 (dd, J1 =8.7 Hz, J2 =2.0 Hz, 2H), 6.40 (d, J= 2.0 Hz, 2H), 7.29 (d, J=8.9 Hz, 2H), 10.76 (s, 2H). 13C NMR (CDCl3, 100.62 MHz): δ = 13.78, 21.66, 22.36, 25.69, 28.8131.60, 53.08, 67.69, 96.84, 101.76, 106.32, 112.19, 127.39, 160.60, 161.84, 165.28, 171.15. IR (KBr): 2921, 2850, 1625, 1590, 1497(s), 1363, 1246, 828 cm-1. Anal. Calcd for C46H70N2NiO6: C, 68.57; H, 8.76; N, 3.48. Found: C, 67.79; H, 8.80; N, 3.52.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]copper(II) (mo3). En2 (136.56 mg, 0.18 mmol) was completely dissolved in a mixture of boiling methanol (15 mL) and chloroform. After the addition of copper(II) acetate monohydrate (36.40 mg, 0.18 mmol) in methanol (5 mL) the mixture was stirred for 3 h under reflux. The reaction solution was concentrated, and the resulting solid was filtered off and washed with methanol and ethanol.Yield: 53.99 mg (0.07 mmol, 37%). IR (KBr): 2922, 2850, 1625, 1591, 1504, 1368, 1242, 1187, 1021, 805, 724, 665 cm-1. Anal. Calcd for C46H70CuN2O6: C, 68.16; H, 8.70; N, 3.46. Found: C, 67.61; H, 8.56; N 3.41.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]palladium(II) (mo4). A solution of en2 (115.11 mg, 0.15 mmol) in CH2Cl2/MeOH (10 mL/10 mL) was treated with a solution of palladium(II) acetate (34.50 mg, 0.15 mmol) in dichloromethane (5 mL). The resulting mixture turned brown, and after 3 h under reflux a green solid was obtained which was filtered and washed with methanol. Yield: 29.45 mg (0.03 mmol, 23%). 1H NMR (CDCl3): δ 0.87 (t, J=6.8 Hz, 6H), 1.26-1.43 (m, 36H), 1.71 (m, 4H), 1.76 (s, 6H), 3.36 (m, 4H), 3.90 (t, J=6.6 Hz, 4H), 5.30 (s, 2H), 6.29 (dd, J1=8.9 Hz, J2=2.5 Hz, 2H), 6.44 (d, J=2.5 Hz, 2H), 7.35 (d, J=8.9 Hz, 2H), 11.61 (s, 2H). 13 C NMR (CDCl3): δ 14.10, 21.25, 22.68, 26.03, 29.14-31.92, 56.24, 68.05, 96.07, 102.30, 107.15, 113.02, 128.25, 161.59, 162.09, 162.60, 170.93. IR (KBr): 2924, 2852, 1627, 1602, 1500, 1463, 1358, 1148, 1246, 775 cm-1. Anal. Calcd for C46H70N2O6Pd: C, 64.73; H, 8.27; N, 3.28. Found: C, 63.98; H, 8.23; N, 3.20.

General Procedure for the Preparation of the Binuclear Complexes. The mononuclear nickel complex (mo1 or mo2) was dissolved with the 6-fold excess of LiOH in boiling ethanol. To this solution an appropriate metal salt precursor in methanol was added. A precipitate occurred very fast. After 30 min the solid was filtered off, washed with methanol, and dried in vacuum.

[N,N-Bis[(4-hexadecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]nickel(II)vanadium(IV)oxide (bin1). mo1 (0.26 g, 0.28 mmol), LiOH (40.24 mg, 1.68 mmol), vanadium(IV)oxide sulfate pentahydrate (97.78 mg, 0.28 mmol). Yield: 176.92 mg (0.18 mmol, 64%). IR (KBr): 2922, 2851, 1597, 1512, 1447, 1184, 1002, 810, 766 cm-1. Anal. Calcd for C54H84N2NiO7V: C, 65.99; H, 8.61; N, 2.85. Found: C, 64.53; H, 8.19; N, 2.98. Langmuir 2009, 25(23), 13606–13613

Article

[N,N-Bis[(4-hexadecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]nickel(II)copper(II) (bin2). mo1 (0.32 g, 0.25 mmol), LiOH (35.93 mg, 1.50 mmol), copper(II) acetate monohydrate (49.92 mg, 0.25 mmol); Yield: 221.43 mg (0.23 mmol, 89%). IR (KBr): 2920, 2850, 1603, 1506, 1447, 1196, 1021, 832, 760 cm-1. Anal. Calcd for C54H84CuN2NiO6: C, 66.22; H, 8.64; N, 2.86. Found: C, 65.99; H, 8.58; N, 2.84.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]nickel(II)vanadium(IV)oxide (bin3). mo2 (207.83 mg, 0.26 mmol), LiOH (32.20 mg, 1.29 mmol), vanadium(IV)oxide sulfate pentahydrate (65.30 mg, 0.26 mmol); Yield: 205.45 mg (0.24 mmol, 91%). IR (KBr): 2921, 2851, 1598, 1510, 1447, 1184, 1000, 810, 768 cm-1. Anal. Calcd for C46H68N2NiO7V: C, 63.46; H, 7.78; N, 3.22. Found: C, 62.39; H, 8.08; N, 3.04.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]nickel(II)manganese(II) (bin4). mo2 (205.30 mg, 0.25 mmol), LiOH (35.70 mg, 0.15 mmol), manganese(II) chloride (31.27 mg, 0.25 mmol); Yield: 107.00 mg (0.20 mmol, 80%). IR (KBr): 2923, 2852, 1604, 1506, 1448, 1350, 1199, 837, 758, 604 cm-1. Anal. Calcd for C46H68MnN2NiO6: C, 64.34; H, 7.98; N, 3.26. Found: C, 64.49; H, 7.81; N, 3.18.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]nickel(II)iron(II) (bin5). mo2 (204.85 mg, 0.25 mmol), LiOH (31.74 mg, 1.27 mmol), iron(II) sulfate heptahydrate (70.41 mg, 0.25 mmol); Yield: 104.03 (0.11 mmol, 46%). IR (KBr): 2923, 2852, 1601, 1505, 1438, 1246, 1193, 1020, 836, 767 cm-1. Anal. Calcd for C46H68FeN2NiO6 3 2 LiOH: C, 60.88; H, 7.77; N, 3.09. Found: C, 60.44; H, 7.61; N, 3.06.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]nickel(II)cobalt(II) (bin6). mo2 (205.30 mg, 0.26 mmol), LiOH (31.81 mg, 1.27 mmol), cobalt(II) acetate tetrahydrate (63.52 mg, 0.26 mmol); Yield: 107.93 mg (0.12 mmol, 49%). IR (KBr): 2922, 2851, 1604, 1507, 1440, 1244, 1197, 839, 763 cm-1. Anal. Calcd for C46H68CoN2NiO7: C, 62.88; H, 7.80; N, 3.19. Found: C, 62.84; H, 7.71; N, 3.23.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]dinickel(II) (bin7). mo2 (204.37 mg, 0.25 mmol), LiOH (31.67 mg, 1.27 mmol), nickel(II) acetate tetrahydrate (63.14 mg, 0.25 mmol); Yield: 143.90 mg (0.16 mmol, 64%). IR (KBr): 2923, 2851, 1602, 1504, 1440, 1198, 1019, 838, 762 cm-1. Anal. Calcd for C46H68N2Ni2O6 3 2 LiOH: C, 60.69; H, 7.75; N, 3.08. Found: C, 60.77; H, 7.65; N, 2.97.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]nickel(II)copper(II) (bin8). mo2 (200.56 mg, 0.25 mmol), LiOH (31.06 mg, 1.24 mmol), copper(II) acetate monohydrate (49.69 mg, 0.25 mmol); Yield: 182.57 mg (0.21 mmol, 85%). IR (KBr): 2920, 2850, 1605, 1507, 1446, 1196, 1023, 830, 760 cm-1. Anal. Calcd for C46H68CuN2NiO6: C, 63.70; H, 7.90; N, 3.23. Found: C, 63.29; H, 7.90; N, 3.15.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3-yl]ethan-1,2-diaminato]nickel(II)palladium(II) (bin9). mo2 (202.17 mg, 0.25 mmol), LiOH (31.28 mg, 1.25 mmol), palladium(II) chloride (44.44 mg, 0.25 mmol); Yield: 161.85 mg (0.17 mmol, 68%). IR (KBr): 2922, 2851, 1591, 1501, 1436, 1246, 1021, 767 cm-1. Anal. Calcd for C46H68N2NiO6Pd 3 2LiOH: C, 57.67; H, 7.36; N, 2.92. Found: C, 57.87; H, 7.24; N 2.85.

[N,N-Bis[(4-dodecyl-2-hydroxyphenyl)-2-buten-1-on-3yl]ethan-1,2-diaminato]nickel(II)platinum(II) (bin10). mo2 (204.59 mg, 0.25 mmol), LiOH (31.69 mg, 1.27 mmol), potassium tetrachloro platinate (105.39 mg, 0.25 mmol); Yield: 227.92 mg (0.22 mmol, 88%). IR (KBr): 2921, 2848, 1588, 1497, 1359, 1247, 1186, 1026, 828 cm-1. Anal. Calcd for C46H68N2NiO6Pt 3 2LiOH: C, 52.78; H, 6.74; N 2.68. Found: C, 51.25; H, 6.58; N, 2.56.

Acknowledgment. We thank K. Kuepper for fruitful discussions and DFG for funding within the SFB 569. DOI: 10.1021/la9019712

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