Design, Synthesis And Properties Of Novel Sandwich-Type Complexes With Porphyrinato And Phthalocyaninato Ligands

Porphyrins and their non-naturally occurring analogues phthalocyanines have been intensively studied over the last few decades due to their wide range of biological relevance and industrial applications. It is also well known that both porphyrinato and phthalocyaninato ligands can form sandwich-type complexes with various rare earth metal ions. These complexes exhibit great potential in the fields of molecular magnets, field effect transistors, molecular-based multibit information storage, non-liner optical materials, liquid crystals and molecular machines owing to the intramolecular π-π interactions and the intrinsic nature of the metal centers. As a result, this class of compounds remains as a current research focus. In this thesis a series of novel sandwich-type complexes with porphyrinato and phthalocyaninato ligands have been designed and synthetized, with their structures and properties well researched. The following three topics are the main research contents:(1) Constructing Sandwich-Type Rare Earth Double-Decker Complexes with N-Confused Porphyrinato and Phthalocyaninato LigandsN-confused porphyrin, an interesting porphyrin isomer, has received considerable attention due to the versatile binding modes and redox states associated with the inverted pyrrole moiety. However, sandwich-type rare earth complexes with NCP ligands have not yet been reported to the best of our knowledge. In this section, reaction of the half-sandwich complexes MⅢ(Pc)(acac)(M=La, Eu, Y, Lu, Dy; Pc=phthalocyaninate; acac=acetylacetonate) with the metal-free N-confused5,10,15,20-tetrakis[(4-tert-butyl)phenyl]porphyrin (H2NTBPP) or its methylated analogue H(CH3)NTBPP in refluxing1,2,4-trichlorobenzene led to the isolation of MⅢ(Pc)(HNTBPP)(M=La, Eu, Y, Lu, Dy) or YⅢ(Pc)[(CH3)NTBPP] in8-16%yield. These represent the first examples of sandwich-type rare earth complexes with N-confused porphyrinato ligands. These complexes were characterized with various spectroscopic methods and elemental analysis. The molecular structures of five of these double-decker complexes were also determined by single-crystal X-ray diffraction analysis. In each of these complexes, the metal center is octa-coordinated by four isoindole nitrogen atoms of the Pc ligand, and three pyrrole nitrogen atoms and the inverted pyrrole carbon atom of the HNTBPP or (CH3)NTBPP ligand, forming a distorted square antiprism. For EuⅢ(Pc)(HNTBPP), the two macrocyclic rings are further bound to a CH3OH molecule through two hydrogen bonds formed between the hydroxyl group of CH3OH with an aza nitrogen atom of the Pc ring and the inverted pyrrole nitrogen atom of the HNTBPP ring, respectively. The location of the acidic proton at the inverted pyrrole nitrogen atom of the protonated double-deckers was revealed by1H NMR spectroscopy. In addation, the magnetic property of DyⅢ(Pc)(HNTBPP) was also studied.(2) Enhancing the Magnetic Performance of Bis(tetrapyrrole) Dysprosium Single-Molecule Magnets through Porphyrin Core ModificationAs one of the most important species of single molecule magnets, multiple(tetrapyrrole) lanthanide multiple-decker SMMs (tetrapyrrole=porphyrin and/or phthalocyanine) in particular the bis(tetrapyrrole) lanthanide double-decker single-molecule magnets (SMMs) have attracted considerable research interests associated with their high stability, good crystallinity, distinct molecular structure, impressive magnetic property, and in turn the relatively easy understanding towards the structure-function relationship. However, efforts paid thus far towards tuning the magnetic properties of specific bis(tetrapyrrole) lanthanide SMMs through molecular design and synthesis over the tetrapyrrole ligand(s) seem to be limited to the modification of the tetrapyrrole peripheral substituents. Trial through the core instead of peripheral modification over the tetrapyrrole ligand has not yet been reported, to the best of our knowledge. In this section, core-modified porphyrin-containing bis(tetrapyrrole) rare-earth sandwich complexes MⅢ(Pc)(XTBPP)[Pc=dianion of unsubstituted phthalocyanine, OTBPP=monoanion of5,10,15,20-(4-ter/-butyl)phenyl-21-oxaporphyrin, STBPP=monoanion of5,10,15,20-(4-tert-butyl)phenyl-21-thiaporphyrin][M=Eu or Dy, X=O or S] were synthesized and structurally characterized for the first time. Changing one of the four porphyrin pyrrole nitrogen atoms to oxygen/sulfur in the mixed ring double-decker molecule results in significantly enhanced single-molecule magnet performance in terms of the obviously increased energy barrier of136and194K for3and4, respectively, in comparison with their porphyrin-containing analogue [(Bu)4N][DyⅢ(Pc)(TBPP)]{TBPP5,10,15,20-tetrakis[(4-tert-butyl)phenyl]porphyrin}(5),40K, and the observation of the magnetic hysteresis loops for the core-modified porphyrin-containing double-deckers represent the first time for the mixed (phthalocyaninato)(porphyrinato) lanthanide SMMs.(3) Influence of Porphyrin Meso-attached Substituent on the SMM Behavior of Dysprosium (Ⅲ) Double-deckers with Mixed Tetrapyrrole LigandsIn comparison with the transition-metal involved SMMs, the lanthanide-based counterparts are of special importance because of their significant magnetic anisotropy arising from the large and unquenched orbital angular momentum. As a consequence, great efforts have been paid for the design and synthesis of lanthanide-based SMMs with continuously improved magnetic properties. Thus far investigations have clearly revealed the important effect of ligand field symmetry on generating anisotropic barriers. It is also well known that the relaxation process is easily affected by very subtle change in the coordination environment around the metal center. However, due to the lack of suitable systems containing a series of isostructural complexes with the same or at least similar coordination symmetry but changeable electronic structure for the lanthanide spin carrier, the exploration towards understanding such kind of effect on the magnetic properties of lanthanide SMMs was retarded. Fortunately, bis(tetrapyrrole) rare earth double-decker complexes provide a good chance to work for this target owing to the facility in modifying the tetrapyrrole ligands in the sandwich molecules. In this section, three sandwich-type neutral unprotonated mixed (phthalocyaninato)(porphyrinato) dysprosium(Ⅲ) double-decker complexes Dy(Pc)(Por)[Por=TCPP, TPP, TBPP; Pc=unsubstituted phthalocyaninate, TCPP=5,10,15,20-tetrakis(4-cyanophenyl) porphyrinate, TPP=5,10,15,20-tetrakis(phenyl) porphyrinate, TBPP=5,10,15,20-tetrakis[(4-/er/-butyl)phenyl] porphyrinate](1-3) have been designed, prepared, and structurally studied. Systematic and comparative studies reveal the slow relaxation of magnetization under both zero and applied dc field for all the three double-deckers, indicating their SMM nature. Stronger quantum tunneling of magnetization (QTM) observed for3in comparison with its two counterparts1and2with similar coordination geometry shows the influence of substituent at the meso-attached phenyl moieties on the magnetic properties.