Tetrathiafulvalene-Supported Triple-Decker Phthalocyaninato Dysprosium(III) Complex: Synthesis, Properties and Surface Assembly

Scientific Reports, Aug 2014

Self-assembly of functional compounds into a prerequisite nanostructure with desirable dimension and morphology by controlling and optimizing intermolecular interaction attracts an extensive research interest for chemists and material scientist. In this work, a new triple-decker sandwich-type lanthanide complex with phthalocyanine and redox-active Schiff base ligand including tetrathiafulvalene (TTF) units has been synthesized, and characterized by single crystal X-ray diffraction analysis, absorption spectra, electrochemical and magnetic measurements. Interestingly, the non-centrosymmetric target complex displays a bias dependent selective adsorption on a solid surface, as observed by scanning tunneling microscopy (STM) at the single molecule level. Density function theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular assemblies, and show that such electrical field dependent selective adsorption is regulated by the interaction between the external electric field and intrinsic molecular properties. Our results suggest that this type of multi-decker complex involving TTF units shows intriguing multifunctional properties from the viewpoint of structure, electric and magnetic behaviors, and fabrication through self-assembly.

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Tetrathiafulvalene-Supported Triple-Decker Phthalocyaninato Dysprosium(III) Complex: Synthesis, Properties and Surface Assembly

Abstract Self-assembly of functional compounds into a prerequisite nanostructure with desirable dimension and morphology by controlling and optimizing intermolecular interaction attracts an extensive research interest for chemists and material scientist. In this work, a new triple-decker sandwich-type lanthanide complex with phthalocyanine and redox-active Schiff base ligand including tetrathiafulvalene (TTF) units has been synthesized, and characterized by single crystal X-ray diffraction analysis, absorption spectra, electrochemical and magnetic measurements. Interestingly, the non-centrosymmetric target complex displays a bias dependent selective adsorption on a solid surface, as observed by scanning tunneling microscopy (STM) at the single molecule level. Density function theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular assemblies, and show that such electrical field dependent selective adsorption is regulated by the interaction between the external electric field and intrinsic molecular properties. Our results suggest that this type of multi-decker complex involving TTF units shows intriguing multifunctional properties from the viewpoint of structure, electric and magnetic behaviors, and fabrication through self-assembly. Introduction With the development of science and technology, the investigation and application of new functional materials have been the main task for production and life. Single-molecule magnets (SMMs) as molecular species exhibiting quantum tunneling and slow magnetic-relaxation processes, have been investigated from the viewpoint of applied science for use in next-generation devices, such as memory storage, quantum computers and spin-based molecular electronics1,2,3,4,5. As a representative, sandwich-type phthalocyaninato and/or porphyrinato lanthanide complexes possess intriguing molecular structures, unique electronic and optical properties due to intramolecular interactions and intrinsic nature of the metal ion6,7,8,9,10,11, rendering them potentially useful in material science, including molecular spintronics, chemical sensors and field-effect transistors12,13,14,15,16. Self-assembly of these functional molecules into a prerequisite nanostructure with desirable dimension and morphology via controlling and optimizing intermolecular interaction has been a subject of extensive research interest for chemists and material scientist17,18,19,20. Recently, the need for new materials with more diversified and more sophisticated properties is continuously increasing. One of the goals is to prepare materials that possess not only one expected property or function but also combine two or more of them in one system. In particular, owing to the important applications in molecular spintronics, the synthesis of novel materials possessing synergy or interplay between electrical conductivity with magnetism has attracted attention in the last few years21,22,23,24,25. Tetrathiafulvalene (TTF) and its derivatives, well-known sulfur-rich organic molecules, are ideally suited as components in these types of systems because they can act as reversible and stable electron donors. Their cationic radical salts constitute an important class of conducting molecular materials26,27,28,29, and have been incorporated as units on molecular machines30,31. Absorbing redox-active TTF organic units on surfaces, and assembling SMMs systems comprised of these molecules with the paramagnetic metal ions may lead to new multifunctional materials with interesting structures and properties26,32,33,34,35,36,37,38,39,40. Herein, we report the synthesis and surface assembly of the first sandwich-type triple-decker lanthanide complex based on a Schiff base ligand containing electrochemically active TTF unit H2L (H2L = 2,2′-((2-(4,5-bis(methylthio)-1,3-dithiol-2-ylidene)-1,3-benzodithiole-5,6-diyl)bis(nitrilomethylidyne)bis(4-chlorophenol)), which extends the classical system of sandwich-type tetrapyrrole oligomers limited to homoleptic or heterolepic phthalocyanine and/or porphyrin lanthanide multi-decker complexes6,7,8,9,10,11. For future applications in molecular electronics or spintronics, such as molecular field-effect transistors or spin field-effect transistors, the introduction of redox-active TTF derivatives will offer opportunities for new multifunctional molecular materials to fabricate single-molecule devices. Results Reaction of phthalocyanine, dysprosium acetylacetonate and TTF-supported Schiff base ligand in a 1:2:2 molar ratio in 1,2-dichloroethane and methanol resulted into the formation of target complex [Dy2(Pc)L2(CH3OH)]·5(ClCH2CH2Cl) (complex 1, Supplementary Fig. S1), which is stable in both solution and solid state, and corresponding characterization has been accomplished by single crystal X-ray diffraction analysis, absorption spectra, electrochemical and magnetic measurements. More interestingly, the assembling behavior of such novel complex was stud (...truncated)


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Feng Gao, Xue-Mei Zhang, Long Cui, Ke Deng, Qing-Dao Zeng, Jing-Lin Zuo. Tetrathiafulvalene-Supported Triple-Decker Phthalocyaninato Dysprosium(III) Complex: Synthesis, Properties and Surface Assembly, Scientific Reports, 2014, Issue: 4, DOI: 10.1038/srep05928