Neutral radical and singlet biradical forms of meso-free, -keto, and -diketo hexaphyrins(1.1.1.1.1.1): effects on aromaticity and photophysical properties

We have investigated the electronic structures and photophysical properties of 5,10,20,25-tetrakis(pentafluorophenyl)-substituted hexaphyrin(1.1.1.1.1.1) (1) and its meso-keto (2) and meso-diketo derivatives (3) using various spectroscopic measurements. In conjunction with theoretical calculations, these analyses revealed fundamental structure-property relationships within this series, including unusual ground-state electronic structures with neutral, monoradical, and singlet biradical character. The meso-free species 1 is a representative 26 π-electron aromatic compound and shows characteristic spectroscopic features, including a sharp Soret band, well-defined Q-like bands, and a moderately long excited state lifetime (τ = 138 ps). In contrast, the meso-keto derivative 2 displays features characteristic of a neutral monoradical species at the ground state, including the presence of lower energy absorption bands in the NIR spectral region and a relatively short excited-state lifetime (13.9 ps). The meso-diketo 3 exhibits features similar to those of 2, specifically NIR absorptions and a short excited-state lifetime (9.7 ps). Compound 3 is thus assigned as being a ground-state singlet biradicaloid. Two photon absorption (TPA) measurements revealed comparatively large σ(2) values of 600 GM for 2 and 1600 GM for 3 with excitation at λ(ex) =1600 nm as compared to that observed for 1 (σ(2): 360 GM). The enhanced nonlinear optical properties of 2 and 3 are rationalized in terms of the open-shell electronic configuration allowing a large, field-induced fluctuation in the electron density (i.e., a large polarization). This interpretation is supported by theoretical evaluations of the static second hyperpolarizabilities (γ) and γ density analyses. Furthermore, nucleus-independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA) values and anisotropy of the induced current density (AICD) plots revealed a clear distinction in terms of the aromatic character of 1-3. Importantly, the open-shell radicaloid 2 and singlet biradicaloid 3 can be formally regarded as 27 π-electron nonaromatic and 26 π-electron aromatic species, respectively, constrained within a dominant 28 π-electron conjugated network. On the basis of the combined experimental and theoretical evidence, it is concluded that the meso-carbonyl groups of 2 and 3 play an important role in perturbing the macrocyclic π-conjugation of the parent hexaphyrin structure 1. In particular, they lead to the imposition of intrinsic radical and biradical character on the molecule as a whole and thus easy-to-discern modifications of the overall electronic effects.     

Electronic state of a conducting single molecule magnet based on Mn-salen type and Ni-dithiolene complexes

The electrochemical oxidation of an acetone solution containing [Mn(III) (5-MeOsaltmen)(H(2)O)](2)(PF(6))(2) (5-MeOsaltmen(2-) = N,N'-(1,1,2,2-tetramethylethylene)bis(5-methoxysalicylideneiminate)) and (NBu(4))[Ni(dmit)(2)] (dmit(2-) = 2-thioxo-1,3-dithiole-4,5-dithiolate) afforded a hybrid material, [Mn(5-MeOsaltmen)(acetone)](2)[Ni(dmit)(2)](6) (1), in which [Mn(2)](2+) single-molecule magnets (SMMs) with an S(T) = 4 ground state and [Ni(dmit)(2)](n-) molecules in a charge-ordered state (n = 0 or 1) are assembled in a layer-by-layer structure. Compound 1 crystallizes in the triclinic space group P1 with an inversion center at the midpoint of the Mn···Mn dimer. The [Mn(2)](2+) unit has a typical nonplanar Mn(III) dimeric core and is structurally consistent with previously reported [Mn(2)] SMMs. The six [Ni(dmit)(2)](n-) (n = 0 or 1) units have a square-planar coordination geometry, and the charge ordering among them was assigned on the basis of ν(C═C) in IR reflectance spectra (1386, 1356, 1327, and 1296 cm(-1)). The [Mn(2)](2+) SMM and [Ni(dmit)(2)](n-) units aggregate independently to form hybrid frames. Electronic conductivity measurements revealed that 1 behaved as a semiconductor (ρ(rt) = 2.1 × 10(-1) Ω·cm(-1), E(a) = 97 meV) at ambient pressure and as an insulator at 1.7 GPa (ρ(1.7GPa) = 4.5 Ω·cm(-1), E(a) = 76 meV). Magnetic measurements indicated that the [Mn(2)](2+) units in 1 behaved as S(T) = 4 SMMs at low temperatures.     

Photocurrent generation from hierarchical zinc-substituted hemoprotein assemblies immobilized on a gold electrode

All connected: a protein-immobilized electrode comprising hierarchical assemblies of photoactive cytochrome b(562) reconstituted with zinc protoporphyrin IX exhibits remarkably enhanced photocurrent generation relative to an electrode bearing a single zinc-substituted hemoprotein layer. The protein oligomers, which bear a covalently linked protoporphyrin group, assemble by a supramolecular heme/heme pocket interaction.     

Fluorescence microscopic investigation on morphological changes of giant multilamellar vesicles induced by amphiphilic additives

Adding an artificial bolaamphiphile to a dispersion of giant multilamellar vesicles (GMVs) made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) induced a cup-shaped deformation in GMVs accompanied by partial extrusion of the inner vesicle; thereafter, the deformed vesicles returned to their original shape. On the other hand, when the artificial bolaamphiphile together with a surfactant was added to the vesicular dispersion, these deformation and reformation dynamics were transmitted from the outer membranes in GMVs to the inner membranes until an intact inner vesicle was extruded out of the outer membrane. The microscopic aspects of these processes were investigated using amphiphiles tagged with individual fluorophores.     

IR-extended photoluminescence mapping of single-wall and double-wall carbon nanotubes

A simple and efficient technique is described for measuring photoluminescence (PL) maps of carbon nanotubes (NTs) in the extended IR range (1-2.3 mum). It consists of preparing an NT/surfactant/gelatin film and measuring PL spectra using a combination of a tunable Ti-sapphire laser excitation and FTIR detection. This procedure has been applied to a wide range of single- and double-wall NTs unveiling chirality and diameter distributions that have so far been very difficult to measure. The problems associated with deducing these distributions are discussed by comparing absorption and PL mapping data for NT samples prepared under different conditions.     

Learners’ level of understanding of the inclusion relations of quadrilaterals and prototype phenomenon

This paper reports on data from investigations on learners’ understanding of inclusion relations of quadrilaterals, building on the ideas from our earlier study (Fujita & Jones, 2007). By synthesising past and current theories in the teaching of geometry (van Hiele's model, figural concepts, prototype phenomenon, etc.), we propose a theoretical model and method to describe learners’ cognitive development of their understanding of inclusion relations of quadrilaterals, and in order to investigate the topic, data are collected from trainee teachers and lower secondary school students. The findings suggest that in general more than half of above average learners are likely to recognise quadrilaterals primarily by prototypical examples, even though they know the correct definition, and this causes them difficulty in understanding the inclusion relations of quadrilaterals.     

Size control of giant unilamellar vesicles prepared from inverted emulsion droplets

The production of giant lipid vesicles with controlled size and structure will be an important technology in the design of quantitative biological assays in cell-mimetic microcompartments. For establishing size control of giant vesicles, we investigated the vesicle formation process, in which inverted emulsion droplets are transformed into giant unilamellar vesicles (GUVs) when they pass through an oil/water interface. The relationship between the size of the template emulsion and the converted GUVs was studied using inverted emulsion droplets with a narrow size distribution, which were prepared by microfluidics. We successfully found an appropriate centrifugal acceleration condition to obtain GUVs that had a desired size and narrow-enough size distribution with an improved yield so that emulsion droplets can become the template for GUVs.     

High-quality generation of a multispot pattern using a spatial light modulator with adaptive feedback

We propose and demonstrate high-quality generation of a uniform multispot pattern (MSP) by using a spatial light modulator with adaptive feedback. The method iteratively updates a computer generated hologram (CGH) using correction coefficients to improve the intensity distribution of the generated MSP in the optical system. Thanks to a simple method of determining the correction coefficients, the computational cost for optimizing the CGH is low, while maintaining high uniformity of the generated MSP. We demonstrate the generation of a 28×28 square-aligned MSP with high uniformity. Additionally, the proposed method could generate an MSP with a gradually varying intensity profile, as well as a uniform MSP consisting of more than 1000 spots arranged in an arbitrary pattern.     

Development of scattering near-field optical microspectroscopy apparatus using an infrared synchrotron radiation source

We report the status of a scattering near-field microspectroscopy apparatus developed at SPring-8 using an infrared synchrotron radiation (IR-SR) source. It consists of a scattering type scanning near-field optical microscope and a Fourier transform infrared spectrometer. The IR-SR is used as a highly brilliant and broad-band IR source. This apparatus has potential for application in near-field spectroscopy with high spatial resolution beyond the diffraction limit. In order to eliminate background scatterings from the probe shaft and/or sample surface, we used higher harmonic demodulation method. The near-field spectra were observed by 2nd harmonic components using the lock-in detection. The spatial resolution of about 300 nm was achieved at around 1000 cm^? 1 (10 μm wavelength).     

Clustering structure of aqueous solution of kinetic inhibitor of gas hydrates

Poly-[N-vinylcaprolactam] (PVCAP) and its related compounds are specific polymeric compounds for inhibiting hydrate formation. To clarify the inhibition mechanism of these compounds on hydrate nucleation at the molecular level, we measured the mass spectra of clusters generated from the fragmentation of liquid droplets including N-methylcaprolactam (NMCAP; functional group of PVCAP). By comparing the mass spectra of clusters of the solutions--pure D2O, tetrahydrofuran (THF)-D2O, NMCAP-D2O, and THF-NMCAP-D2O--it was found that the interaction of NMCAP with D2O was much stronger than that of THF with D2O. The relative intensity ratio of D+(NMCAP)m(D2O)n clusters to all the clusters observed for the NMCAP-D2O (1:250) mixed solution was 0.45. On the other hand, the relative intensity ratio of D+(THF)1(D2O)n clusters to all the clusters observed for the THF-D2O (1:17) mixed solution was 0.15. In the case of the THF-NMCAP-D2O three-component mixed solution, the NMCAP-D2O interaction was more predominant than the THF-D2O interaction, even at a lower NMCAP concentration. NMCAP reduces free mobile water molecules around NMCAP, but THF does not. This correlates with the facts that THF forms its hydrate below the freezing point and that PVCAP works as an inhibitor of gas hydrates.