Highly Efficient Spectral Measurement Methods Using Newly Developed High-Throughput Magnetic Circularly Polarized Luminescence System.

Magnetic circularly polarized luminescence (MCPL) spectroscopy is widely used to evaluate the luminescence dissymmetry factor (g) for compounds. However, even for the same instrument and operating conditions, the measured g is affected by errors associated with sources such as baseline drift and spectral noise, and so the range of variation of g must be considered when comparing values, which requires multiple measurements for the same sample. Also, because many samples undergo photodegradation under excitation light, it is difficult to accumulate and average spectra for samples with weak MCPL signals to improve the signal-to-noise ratio.

Identification of a Weak Interaction between the Spin-Only 4f-Electronic System of Trivalent Gd Ion and a Photoexcited Cyclic π Electronic System.

An electronic interaction between the spin-only 4f-electronic system and the photoexcited π cyclic system has been identified in the anionic bis(phthalocyaninato)gadolinium(III) complex [PcGd] by using variable-temperature variable-magnetic-field magnetic circular dichroism (VTVH MCD). Two positive MCD -term patterns, corresponding to the Q and Q absorption bands, were observed to increase in intensity as the temperature decreased, indicating a ferromagnetic-type interaction between spin angular momentum of the 4f system and orbital angular momentum of the photoexcited π system. A theoretical model incorporating the - interaction constant was fitted to the VTVH MCD spectra, confirming the presence of a weak interaction, whose intensity was determined as = 0.

Construction of high-throughput magnetic circular dichroism measurement system and its application to research on magnetic and optical properties of phthalocyanine complexes.

Magnetic circular dichroism (MCD) spectroscopy is a powerful method for evaluating the electronic structure and magnetic and optical properties of molecules. In particular, MCD measurements have been performed on phthalocyanines and porphyrins with various central metal ions, axial ligands, and substituents to elucidate their properties. It is essential to develop a robust high-throughput technique to perform these measurements comprehensively and efficiently.

Tuning of the antiferromagnetic-type interaction in photo-excited single-decker porphyrin-lanthanide complexes with different crown capping ligands.

The magnetic interaction between the total angular momentum () of the 4f electrons in a lanthanide ion and the orbital angular momentum () of a porphyrin in the photo-excited states of 5,10,15,20-tetraphenylporphyrinato Dy(III) complexes capped with a crown ether with one of two different symmetries, 12-crown-4 or 1-aza-12-crown-4, was investigated by temperature- and magnetic dependent magnetic circular dichroism (VT-VH MCD). The analysis was conducted on the complexes with different non-aromatic ligands to investigate how different symmetries of the non-aromatic ligands have an impact on the electronic interaction causing an anti-parallel orientation of and . The magnitude of the - interaction was determined from simulation-based fitting to experimental ratios.

Electronic structure analysis of phthalocyanine complexes using magnetic circular dichroism and magnetic circularly polarized luminescence spectroscopy.

In the study of phthalocyanine complexes using magnetic circular dichroism (MCD) spectroscopy, the electronic structure of excited states is generally discussed based on the rigid-shift approximation, in which the band profiles for left-handed circularly polarized (lcp) and right-handed circularly polarized (rcp) light are assumed to be the same. This assumption may not necessarily be valid for cases where there are multiple initial states having different geometries. Magnetic circularly polarized luminescence (MCPL) from phthalocyanine complexes can be regarded as an example of such cases, since the two degenerate emission states are split in a magnetic field and can undergo a structural deformation.

Magnetic interaction of photoexcited terbium-porphyrin complexes with non-aromatic ligands having different symmetries.

Interaction between the total angular momentum () of 4f electrons in lanthanides and the orbital angular momentum () of porphyrins in the photoexcited states was investigated by temperature-dependent and magnetic circular dichroism (MCD) for 5,10,15,20-tetraphenylporphyrinato (TPP) terbium(III) complexes with two different non-aromatic ligands 12-crown-4(1,4,7,10-tetraoxacyclododecane) and 1-aza-12-crown-4(1,4,7-trioxa-10-azacyclododecane). The two cases with different ligands were examined in order to understand how magnetic interaction depends on the symmetry of the non-aromatic ligands. The three absorption bands in the visible region, B(0,0), Q(1,0), and Q(0,0) bands, showed temperature-dependent MCD A term.

Antiparallel Coupling between a 4f System and a Photoexcited Cyclic π System in a Dysprosium(III) Monoporphyrinato Complex.

Magnetic coupling resulted by an orbital angular momentum of a photoexcited cyclic π-conjugated system and total angular momentum of a localized 4f electronic system in [Dy(TPP)(cyclen)]Cl (TPP = 5,10,15,20-tetraphenylporphyrinato; cyclen = 1,4,7,10-tetraazacyclododecane) has been identified using magnetic circular dichroism (MCD). The MCD A-term patterns of the compound show a negative increment in the intensity by decreasing temperature and nonproportionality to the magnetic field. This phenomenon is experimentally observed for the first time in porphyrin-based lanthanide complexes and indicates the presence of the - interaction, with the preferred orientation being antiparallel.

Intramolecular Magnetic Interaction in a Photogenerated Dual Angular Momentum System in a Terbium-Phthalocyaninato 1:1 Complex.

Intramolecular magnetic interaction between a localized open-shell 4f-electronic system and a photoexcited macrocyclic π-conjugate system in terbium-phthalocyaninnato (Tb-Pc) 1:1 complex was investigated using variable-temperature variable-field magnetic circular dichroism (VTVH MCD) spectroscopy. The 1:1 complex [Tb(Pc)(cyclen)]Cl (Pc = phthalocyaninato dianion, cyclen = 1,4,7,10-tetraazacyclododecane) with the capping ligand providing an exact fourfold symmetry showed a significant temperature dependence and a nonlinear field dependence in the MCD intensity of the Pc-centered highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) π-π* transition, while a diamagnetic congener [Y(Pc)(cyclen)]Cl showed a temperature-independent MCD with a linear-field dependence. This indicates that the (4f) system of the Tb ion with a total angular momentum and the photoexcited π-system of the Pc macrocycle with an orbital angular momentum are magnetically coupled.

Spectroscopic Investigation of Interaction between the 4f Electronic System and the Photoexcited Cyclic π System in Terbium(III) Monoporphyrinato Complex.

Electronic interaction between the total angular momentum () of the 4f electronic system and an angular momentum () of the photoexcited cyclic π system in a terbium(III) monoporphyrinato complex with a capping ligand cyclen, [Tb(TPP)(cyclen)]Cl (TPP = 5,10,15,20-tetraphenylporphyrinato; cyclen = 1,4,7,10-tetraazacyclododecane), have been investigated by varied-temperature and varied-magnetic-field magnetic circular dichroism (MCD) spectroscopy. Three MCD A-term patterns which correspond to B(0,0), Q(0,0), and Q(1,0) absorption bands were observed for the complex which was incorporated into a thin film of poly(methyl methacrylate), PMMA, as well as that in solution phase. The A-term patterns in the Soret band region and Q-band region were found to show opposite behavior with changes in temperature and magnetic field.

Determination of ligand field splitting in lanthanide(iii) monoporphyrinato complexes.

The 4f-electronic structures of the ground multiplet states of a series of lanthanide(iii) monoporphyrinato complexes with a cyclen as the capping ligand [Ln(TPP)(cyclen)]Cl (Ln = Tb, Dy, Ho, Er, Tm, and Yb; TPP = 5,10,15,20-tetraphenylporphyrinato; cyclen = 1,4,7,10-tetraazacyclododecane) have been determined using experimental NMR and magnetic susceptibility data. Magnetic susceptibilities of the microcrystalline samples of [Ln(TPP)(cyclen)]Cl were measured in the range of 1.8-300 K.

Synthesis of a Series of Heavy Lanthanide(III) Monoporphyrinato Complexes with Tetragonal Symmetry.

A series of heavy lanthanide(III) and yttrium(III) monoporphyrinato complexes formulated in [Ln(TPP)(cyclen)]Cl (Ln = Tb, Dy, Ho, Er, Tm, Yb, and Y; TPP = 5,10,15,20-tetraphenylporphyrinato), with cyclen, 1,4,7,10-tetraazacyclododecane, as a capping ligand, have been prepared in mild conditions and studied using single-crystal X-ray diffraction crystallography. The complexes exhibit an electronic absorption band (B(0,0)) in the range of 421-423 nm, showing a bathochromic shift associated with the increase of the ionic radii of the lanthanide, as well as two peaks of Q(1,0) and Q(0,0) bands between 548-586 nm. All of the complexes are isostructural, where both TPP and cyclen are coordinated to a lanthanide(III) or yttrium(III) ion giving an eight-coordinate square-antiprismatic (SAP) geometry (average skew angles are in the range of 43.