Phthalocyaninato Rare Earth Research Articles

1H NMR spectral analysis of structural features in a series of paramagnetic homoleptic binuclear triple-decker phthalocyaninato lanthanide complexes

The search for efficient methods of comparative structural investigations of coordination compounds in solid state and solutions is a very relevant task. In this study, structural assignments in a series of Ln2[(15C5)4Pc]3 complexes (where [(15C5)4Pc]2- is 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninato-dianion, Ln = Nd3+, Tb3+, Dy3+, Ho3+, Er3+ and Tm3+) was performed using NMR relaxation and paramagnetic lanthanide-induced shifts (LIS) data. Analysis of the paramagnetic chemical shifts and relaxation rates evidenced of isostructurality of the complete series of the investigated triple-decker complexes in the solutions. The performed systematic DFT calculations for a series of model complexes with methoxy-substituted ligands Ln2[(MeO)8Pc]3 demonstrate that the calculated geometrical factors are in agreement with characteristics extracted from experimental NMR data.

Self-assembled monolayers of polyoxovanadates with phthalocyaninato lanthanide moieties on gold surfaces.

The two first representatives of phthalocyaninato (Pc) lanthanide-ligated polyoxovanadate cages {[V12O32(Cl)](LnPc)n}n-5 (n = 1 or 2, Ln = Yb3+) were synthesised and fully characterised. These magnetic complexes form two-dimensional self-assembled monolayers exhibiting electrical conductivity on gold substrate surfaces, as assessed by using an EGaIn tip.

Phthalocyaninato lanthanide(iii) acetates as a new class of molecular paramagnets with large magnetocaloric effect

Lanthanide( iii ) ions situated in a coordination site of phthalocyanine macrocycle as molecular paramagnets with a large magnetocaloric effect at the temperatures close to room are presented for the first time on the examples of gadolinium and thulium.

Spin and charge dynamics in[TbPc2]0and[DyPc2]0single-molecule magnets

Magnetization, AC susceptibility and $\mu$SR measurements have been performed in neutral phthalocyaninato lanthanide ([LnPc$_2]^0$) single molecule magnets in order to determine the low-energy levels structure and to compare the low-frequency spin excitations probed by means of macroscopic techniques, such as AC susceptibility, with the ones explored by means of techniques of microscopic character, such as $\mu$SR. Both techniques show a high temperature thermally activated regime for the spin dynamics and a low temperature tunneling one. While in the activated regime the correlation times for the spin fluctuations estimated by AC susceptibility and $\mu$SR basically agree, clear discrepancies are found in the tunneling regime. In particular, $\mu$SR probes a faster dynamics with respect to AC susceptibility. It is argued that the tunneling dynamics probed by $\mu$SR involves fluctuations which do not yield a net change in the macroscopic magnetization probed by AC susceptibiliy. Finally resistivity measurements in [TbPc$_2]^0$ crystals show a high temperature nearly metallic behaviour and a low temperature activated behaviour.

Molecular structure of phthalocyaninato lanthanide LnPc(OAc) complexes derived from the FTIR and FT Raman studies

Room temperature Fourier transform IR and Raman spectra in the range 30–4000 cm−1 and 80–4000 cm−1 of Dy, Ho, Er and Lu phthalocyanide PcLn(OAc)-type complexes have been measured, respectively. The assignment of the bands observed has been made on the literature data. The molecular structure of the PcLnX-type derivatives has been discussed on the basis of the group theory taking into account the shape and number of the bands corresponding to the stretching and bending vibrations of the LnN4O coordination polyhedron as well as whole PcLn(OAc) complex.

Single Molecule Magnet with Single Lanthanide Ion

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Single molecule magnet with single lanthanide ion

The single molecule magnet behavior of metal complexes containing a single magnetic ion was first reported for phthalocyaninato–lanthanide complexes with a “double-decker” structure. In this paper, recent attempts by the author and coworkers at revealing the magnetism and electronic structures of the mononuclear and dinuclear lanthanide complexes with phthalocyaninato ligands are reviewed.

Templated tetramerization of dicyanobenzenes to form mixed porphyrinato and phthalocyaninato rare earth(III) triple-decker complexes

Heteroleptic porphyrinato/phthalocyaninato rare earth(III) triple-decker compounds M 2( Por )2( Pc ') (1a-4a) and M 2( Por )( Pc ')2 (1c-4c) ( M = Eu , Tb ; Por = TDOPP , Pc ' = OOPc or Por = TpClPP , Pc ' = Pc where H 2(TDOPP) = 5,10,15,20-tetrakis(4-n-dodecyloxyphenyl)porphyrin, H2[OOPc] = 2,3,9,10,16,17,23,24-octakis(n-octyloxy)phthalocyanine, H 2(TpClPP) = 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin, H 2( Pc ') = general phthalocyanine, and H 2( Pc ) = unsubstituted phthalocyanine) were obtained by the cyclic tetramerization of the corresponding dicyanobenzenes 7 using monoporphyrinato rare earth(III) acetylacetonates M(Por)acac as templates with catalysis by the organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Double-decker complexes M(Por)(Pc') ( M = Eu , Tb ; Por = TDOPP , Pc ' = OOPc or Por = TpClPP , Pc ' = Pc ) (1b-4b) were isolated as side products. For the purpose of comparative study, homo- and hetero-dinuclear rare earth triple-deckers with one porphyrinato and two phthalocyaninato ligands M2(Por)( Pc ')2 (1c, 2c) ( M = Eu , Tb ; Por = TDOPP , Pc ' = OOPc ) and ( Por ) M ( Pc ') M '( Pc ')( M ≠ M ' = Eu , Tb ) (5c, 6c) were also prepared using the raise-by-one-story method. The complexes were characterized by UV-vis, near-IR, IR and mass spectra. The comparison between 1 H NMR spectra of the two series of triple-decker compounds a and c, and also between the substituted phthalocyanine- and unsubstituted phthalocyanine-containing europium triple-deckers, renders it possible to assign the aromatic proton signals unambiguously.

Distinction between Light and Heavy Lanthanide(III) Ions Based on the 1H NMR Spectra of Heteroleptic Triple-Decker Phthalocyaninato Sandwich Complexes

The 1H NMR spectra of two series of heteroleptic triple-decker phthalocyaninato sandwich complexes of the rare earth(III) ions have been recorded. The ligands comprise unsubstituted phthalocyanine (Pc) and 2,3,9,10,16,17,23,24-octakis(1‘-octyloxy)phthalocyanine (Pc*), and the complexes are of the form PcMPc*MPc (series 1) and PcMPc*MPc* (series 2), where M = Pr − Tm (except Pm, Gd). In some cases, the homoleptic complexes Pc*MPc*MPc* (series 3) were also available. The chemical shifts of five proton positions in series 1, and 10 positions in series 2 were compared with the shifts for the analogous complexes of the diamagnetic yttrium(III) ion. The experimental lanthanide-induced shifts (LIS) were separated into the contact and dipolar contributions using the crystal-field dependent methods of Reilley and co-workers. This work represents the first analysis of LIS in triple-decker phthalocyaninato lanthanide complexes. The results showed a dominance of dipolar contributions but also revealed that contact influences cannot be ignored, even for protons located in the peripheral alkoxy substituents. Analysis by graphical and matrix methods indicates that there is a clear discontinuity in the data between terbium and dysprosium, whereby the metals Nd, Sm, Eu and Tb possess a positive hyperfine coupling term Fi, and the later metals Dy, Ho (limited data), Er and Tm require a negative contact term. This change is coincident with a near-halving of the dipolar term Gi·A20〈r2〉 for the later metals. The properties of praseodymium are anomalous, in that its complexes are readily demetalated, and its NMR behavior places it in the second group of metal ions, despite its early position in the lanthanide series. Use of crystal-field independent analysis shows that the discontinuity near the middle of the series is related to variation in both the hyperfine electron−nuclear coupling constant and the crystal-field properties of the metal ions, rather than to gross changes in geometry.

Electronic Structures of Metal Complexes Possessing Stacking Configurations of Conjugated Macrocycles.

Electronic structures of multilayered phthalocyanine (H2pc) complexes, including phthalocyaninato lanthanide double-decker complexes (dimers), triple-decker complexes (trimers), their radicals, and a tetramer biradical, were investigated through spectroscopic measurements, synthesis of new complexes and theoretical calculations. (1) Excited states of double-decker phthalocyaninato complexes were described using exciton-type and charge-resonance-type excitations. Assignments were given for split Q bands and B bands of lanthanide and tin phthalocyaninate dimers. (2) A new soluble crown-ether substituted trimer was synthesized to obtain detailed spectroscopic data. Previously unknown absorption bands were found in near IR region. The changes in the electronic spectra from a monomeric phthalocyaninato complex through the trimeric complex were accounted for. (3) In order to describe electronic structure of molecular assembly systems in a manner where roles of component units are explicitly represented, localized orbitals (LOs) defined to have a maximum population on a unit were used. The LOs were employed for CI calculations, thereby contributions of intra- and inter-ligand excitation s in excited states of the dimer and trimer were elucidated. Orbital energy changes on respective macrocycies of the dimer and trimer were evaluated using the LOs. (4) A hole in a radical species of the dimer was concluded to be delocalized over the macrocycles by a comparison of electronic spectra of a newly synthesized hetero-dimer, [Lu (nc) (pc) ] (H2nc: naphthalocyanine), and two homo-dimers. Based on the hole delocalization, a description of ground and excited states of the dimer radicals was given. (5) A trimer radical generated by chemical oxidation showed an intense band at 5000 cm-1. Energy ratio of the band to the counterpart of the dimer (ca.1/√2 ) as well as the difference of the behavior of the hole was explained. The model also correctly predicted the presence of a single intense band in Q-band region. (6) From a newly synthesized crown-ether substituted dimer radical, a supramolecular structure consisting of two dimer radicals was generated. It was shown from electronic and ESR spectra that the supramolecular structure was in biradical state where the two holes are localized on respective dimer sites.