Optical Property Control by the Interligand Charge Transfer Excited State in Brominated Homoleptic and Heteroleptic Aluminum Dinuclear Triple-Stranded Helicates.

The utilization of aluminum, an abundant and inexpensive element, for the synthesis of novel functional complexes is extremely important, but the design and control of photofunctionality are still unexplored. In this study, we focused on our previously developed dinuclear triple-stranded helicates incorporating two aluminum ions (ALPHY) to synthesize both homoleptic and heteroleptic complexes with bromine atoms at the 3-position of the pyrrole moiety in the Schiff base ligands. The brominated Schiff base ligands were reacted with AlCl3 to synthesize homoleptic complexes, while different ligands were mixed to prepare heteroleptic complexes. Single-crystal X-ray structural analysis revealed the structures of these novel complexes. We found that increasing the degree of bromination resulted in a tunable emission color, shifting progressively from 550 (yellow) to 566 nm (orange). Optical resolution of the complexes facilitated the observation of mirror-image circular dichroism and circularly polarized luminescence. Furthermore, employing ultrafast spectroscopy techniques, we have elucidated that the optical properties are governed by the interligand charge transfer (ILCT) among the three ligands. The formation of heteroleptic complexes induces the ILCT state even in nonpolar environments, thereby accelerating nonradiative decay and intersystem crossing. These findings mark significant advancements in photofunctional materials based on multinuclear complexes.

Unraveling the Remarkable Influence of Substituents on the Emission Variation and Circularly Polarized Luminescence of Dinuclear Aluminum Triple-Stranded Helicates.

This study explored the development of functional dyes using aluminum, focusing on aluminum-based dinuclear triple-stranded helicates, and examined the effects of substituent variations on their structural and optical properties. Key findings revealed that the modification of methyl groups to the pyrrole positions significantly extended the conjugation system, resulting in a red shift in the absorption and emission spectra. Conversely, the modification of methyl groups at the methine positions due to steric hindrances increased the torsion angle of the ligands, leading to a blue shift in the absorption and emission spectra. A common feature across all complexes was that in the excited state, one of the three ligands underwent significant structural relaxation. This led to a pronounced Stokes shift and minimal spectra overlap with high photoluminescence behaviors. Moreover, our research extended to the optical resolution of the newly synthesized complexes by analyzing the chiroptical properties of the resulting enantiomers, including their circular dichroism and circularly polarized luminescence. These insights offer valuable contributions to the design and application of novel aluminum-based functional dyes, potentially influencing a range of fields, from materials science to optoelectronics.

Fast and artifact-free circular dichroism measurement of solid-state structural changes.

A novel chiroptical spectrophotometer, Multichannel (MC)-circular dichroism (CD), which does not require a wavelength scan and provides artifact-free CD spectra in seconds, was developed by solving the incompatibility problem between data acquisition and modulation timescales. The design and instrumentation are compared with the Universal Chiroptical Spectrophotometer (UCS)-1, which can measure artifact-free CD spectra in the solid state. Enantiomeric single crystals composed of achiral components, α-Ni(H2 O)6 ・SO4 , and achiral films with substantial macroscopic anisotropies were measured on both MC-CD and UCS-1 and compared.

Highly Fluorescent Bipyrrole-Based Tetra-BF2 Flag-Hinge Chromophores: Achieving Multicolor and Circularly Polarized Luminescence.

This study reports the facile syntheses of tetra-boron difluoride (tetra-BF2 ) complexes, flag-hinge-like molecules that exhibit intense green-to-orange luminescence in solution and yellow-to-red emission in the solid states. Single-crystal structure analysis and density functional theory calculations suggested a bent structure of this series of compounds. The complexes also exhibited excellent optical properties, with quantum yields reaching 100 % and a large Stokes shift. These properties were attributed to the altered bending angle of the molecule in the S1 excited state. As the rotational motion was suppressed around the 2,2'-bipyrrole axis, atropisomers with axial chirality were formed, which are optically resolvable into (R) and (S)-enantiomers through a chiral column. The atropisomers thus function as circularly polarized luminescent (CPL) materials, in which the color (green, green-yellow, and yellow) can be varied by controlling the aggregation state. This rational design of multi-BF2 complexes can potentially realize novel photofunctional materials.

Dinuclear Triple-Stranded Helicates Composed of Tetradentate Ligands with Aluminum(III) Chromophores: Optical Resolution and Multi-color Circularly Polarized Luminescence Properties.

New chiroptical chromophores, dinuclear triple-stranded helicates, composed of tetradentate ligands with aluminum(III) ions, are described. These are synthesized in two steps using inexpensive pyrrole derivatives, hydrazine, and aluminum chloride. These molecular architectures (ALPHY) show multi-color (cyan, yellow, and orange) photoluminescence in solution and in the solid-state, which depends on the substituents of the ligands. The photoluminescence quantum yields of helicates were up to 54 %. The right-handed (P) and left-handed (M) helicates are so stable that they do not undergo racemization in some solvents and are mirror images according to circular dichroism and circularly polarized luminescence (CPL) with an absolute luminescence dissymmetry factor (glum ) of up to the 10-3 order. Mixing the different helicates produces white-light emission with CPL characters. This study offers a glimpse into the potential applications of chromophores with diverse photophysical properties.

Decomposition of amyloid fibrils by NIR-active upconversion nanoparticles.

We demonstrate amyloid fibril (AF) decomposition induced by NIR-active upconversion nanoparticles complexed with photosensitisers. The process is triggered by upconversion, which initiates a photochemical reaction cascade that culminates in the generation of the highly reactive singlet-oxygen product 1O2 close to the amyloid superstructures, resulting in AF decomposition.

Combined Experimental and Theoretical Studies on Planar Chirality of Partially Overlapped C2-Symmetric [3.3](3,9)Dicarbazolophanes.

Partially overlapped dicarbazolophanes exhibit a planar chirality. In this study, C2-symmetrical [3.3](3,9)dicarbazolophane derivatives (CZ1-CZ3) have been optically resolved by preparative chiral high-performance liquid chromatography for the first time. In their circular dichroism (CD) spectra, moderate Cotton effects (CEs) were observed for their 1Lb and 1La transitions (|Δε| = 10-12 and 51-57 M-1 cm-1, respectively), while intense CEs were notified in their 1B transitions (|Δε| = 156-216 M-1 cm-1), absorption dissymmetry (gabs) factors being in orders of 10-2. Circularly polarized luminescence spectrum was also obtained for cyanamide derivative CZ1, with a comparative luminescence dissymmetry (glum) factor of 0.013. A computational investigation was applied to address the factors for such remarkable chiroptical responses in these dicarbazolophanes of planar chirality. Absolute configurations were unambiguously determined by the comparison of experimental and theoretical CD spectra, which was affirmed by the X-ray crystal structural analysis of enantiomerically pure sulfonamide derivative CZ2.

Characterization and pharmacokinetic evaluation of microcomposite particles of alpha lipoic acid/hydrogenated colza oil obtained in supercritical carbon dioxide.

The work reported here is an extension of our previous findings in which supercritical composite particles (SCP) of alpha lipoic acid (ALA) masked with hydrogenated colza oil (HCO) named as ALA/HCO/SCP were obtained by the modified particles from gas-saturated solutions (PGSS) process in supercritical carbon dioxide in order to obscure the unpleasant taste and odor of ALA. The masking effect on ALA/HCO/SCP was compared with the widely used mechano-chemically masked formulation of ALA and HCO named as MC-50F. In the present study, ALA/HCO/SCP particles were found to have a significant improvement in regard to bitterness, numbness, and smell compared to ALA bulk powders suggesting they were well coated. The pharmacokinetic parameters for ALA/HCO/SCP and ALA bulk powder gave similar values but were significantly different from those of MC-50F. The amount of ALA absorbed into the body, in the administered ALA/HCO/SCP, was comparable to that absorbed by ALA bulk powder, whereas about half portion of ALA of the MC-50F was not absorbed, because the ALA/HCO/SCP particles were small enough and the particles of MC-50F were relatively large and had smaller specific surface area. Therefore, this study suggested a newly masked candidate may offer functional particles with maintained efficacy.

Long-Time Relaxation of Stress-Induced Birefringence of Microcrystalline Alkali Halide Crystals.

Alkali halide single crystals are most commonly used as the diluent matrix in the tablet method or disk technique for spectroscopic measurements. However, stress-induced birefringence (SIB) of alkali halides as well as intrinsic birefringence manifest during the disk formation process. Thus, the true chiroptical measurement is disturbed by optical anisotropies (OA) containing SIB and intrinsic birefringence, except in the case of optical homogeneity. SIB is generally larger than intrinsic birefringence and has a value of several thousand millidegrees in the ultraviolet-visible wavelength range, although this varies with disk type. Here, to investigate the SIB origin, alkali halide crystals were examined using polarized light, X-ray diffraction, Fourier-transform infrared, and electron backscattering diffraction spectroscopic measurements. It was found that, after stress release, the SIB exhibited nonlinear long-time relaxation, which roughly converged within several hours, with the only time-invariant intrinsic birefringence remaining being due to OA. This behavior was strongly related to an increase in the quasi-amorphous domain and the generation of an air gap between the crystallite boundaries and their pellets. Further, a straightforward correlation was found between amorphization and an increase in the disk water content caused by deliquescence. Thus, the OA of alkali halide single crystals was found to have two different origins yielding intrinsic birefringence and SIB.

Gas-saturated solution process to obtain microcomposite particles of alpha lipoic acid/hydrogenated colza oil in supercritical carbon dioxide.

Alpha lipoic acid (ALA), an active substance in anti-aging products and dietary supplements, need to be masked with an edible polymer to obscure its unpleasant taste. However, the high viscosity of the ALA molecules prevents them from forming microcomposites with masking materials even in supercritical carbon dioxide (scCO2). Therefore, the purpose of this study was to investigate and develop a novel production method for microcomposite particles for ALA in hydrogenated colza oil (HCO). Microcomposite particles of ALA/HCO were prepared by using a novel gas-saturated solution (PGSS) process in which the solid-dispersion method is used along with stepwise temperature control (PGSS-STC). Its high viscosity prevents the formation of microcomposites in the conventional PGSS process even under strong agitation. Here, we disperse the solid particles of ALA and HCO in scCO2 at low temperatures and change the temperature stepwise in order to mix the melted ALA and HCO in scCO2. As a result, a homogeneous dispersion of the droplets of ALA in melted HCO saturated with CO2 is obtained at high temperatures. After the rapid expansion of the saturated solution through a nozzle, microcomposite particles of ALA/HCO several micrometers in diameter are obtained.

Far-red fluorescence and chiroptical properties of pyrrolopyrrole aza-BODIPYs induced by the B,O-chelation.

A titanium-mediated aza-BODIPY synthesis using diketopyrrolopyrrole bearing o-anisyl substituents provided B,O-chelated pyrrolopyrrole aza-BODIPYs in a one-pot manner via ether bond cleavage and chelation of the resulting nucleophilic oxygen to the boron atom. The B,O-chelation not only induces the redshifts of absorption and fluorescence but also endows chiroptical properties.

Simultaneous discovery of chiral and achiral dyes: elucidating the optical functions of helical and flag-hinged boron tetradentate complexes.

The construction of novel complexes can lead to the manifestation of unexpected structures and properties, thereby making chemical exploration in experiments a potential source for novel discoveries. In this study, by reacting 6,6'-dihydrazineyl-2,2'-bipyridine with acyl chlorides and subsequently coordinating with boron trifluoride, two different boron-tetradentate ligand complexes were simultaneously generated. One of these complexes exhibited a unique structure in which tetra-BF2 moieties coordinated to all four coordination sites of the ligand molecule, forming a flag-hinged structure around the bipyridine part. The second complex featured a helical structure formed by the hybridization of two BF2 and one B-O-B moieties, representing a highly unusual form of the complex. The structures of these two boron complexes were consistently observed when various substituted acyl chlorides were employed. Furthermore, it was found that enhancing electron-donor properties could induce a redshift in emissions. Utilizing the dimethylamino group as the proton receptor promoted a yellow-to-blue fluorescence switch in the tetra-BF2 complex and an OFF/ON fluorescence in the B-O-B bridged complex upon protonation. The helical chirality observed in the latter complex resulted in stable (P)/(M)-enantiomers after optical resolution. This complex exhibited circular dichroism with a |gabs| of up to 1.2 × 10-2 and circularly polarized luminescence with a |glum| on the order of 10-3 in solution and polymer film.

Fabrication of a Floatable Micron-Sized Enzyme Device Using Diatom Frustules.

Immobilization of enzymes has been widely reported due to their reusability, thermal stability, better storage abilities, and so on. However, there are still problems that immobilized enzymes do not have free movements to react to substrates during enzyme reactions and their enzyme activity becomes weak. Moreover, when only the porosity of support materials is focused, some problems such as enzyme distortion can negatively affect the enzyme activity. Being a solution to these problems, a new function "floatability" of enzyme devices has been discussed. A "floatable" micron-sized enzyme device was fabricated to enhance the free movements of immobilized enzymes. Diatom frustules, natural nanoporous biosilica, were used to attach papain enzyme molecules. The floatability of the frustules, evaluated by macroscopic and microscopic methods, was significantly better than that of four other SiO2 materials, such as diatomaceous earth (DE), which have been widely used to fabricate micron-sized enzyme devices. The frustules were fully suspended at 30 °C for 1 h without stirring, although they settled at room temperature. When enzyme assays were performed at room temperature, 37, and 60 °C with or without external stirring, the proposed frustule device showed the highest enzyme activity under all conditions among papain devices similarly prepared using other SiO2 materials. It was confirmed by the free papain experiments that the frustule device was active enough for enzyme reactions. Our data indicated that the high floatability of the reusable frustule device, and its large surface area, is effective in maximizing enzyme activity due to the high probability to react to substrates.

Correction to "Fabrication of a Floatable Micron-Sized Enzyme Device Using Diatom Frustules".

[This corrects the article DOI: 10.1021/acsomega.3c02104.].

Homochiral 1D helical chain based on an achiral Cu(II) complex.

Self-assembly of an achiral [Cu(L)] complex produced a homochiral helical chain [Cu(L)](3)·2H(2)O (1) (L = 2-dimethylaminoethyl(oxamato)). Interestingly, complex 1 obtained in our laboratory exhibits only a left-handed helical chain without any chiral source. Single-crystal X-ray analysis revealed the absolute structure and homochirality of its helical chain structure in the space group of P3(2). Solid-state circular dichroism (CD) spectra confirmed the high enantio excess of the crystals obtained in different synthesis batches. Magnetic susceptibility measurements reveal a relatively strong intrachain antiferromagnetic interaction between Cu(II) centers via an oxamato bridge (J = -74.4 cm(-1)).

Chiroptical spectra of tetrakis (+)-3-heptafluorobutylrylcamphorate Ln(III) complexes with an encapsulated alkali metal ion: solution structures as revealed by chiroptical spectra.

The preparation of tetrakis((+)-hfbc) lanthanide(III) complexes with an encapsulated alkali metal and ammonium ions M[Ln((+)-hfbc)(4)] (hereafter abbreviated as M-Ln : (+)-hfbc, (+)-heptafluorobutyrylcamphorate; M, ammonium or benzyl ammonium ions as well as alkali metal ions) was reported and discussed. The electronic circular dichroism (CD) spectra in the intraligand π-π* transition of M-Ln were examined in view of the solvent effect. Here, the concentration, alkali metal, and ammonium ion dependences are compared with the solid CD, (5)D(0)←(7)F(0) (Eu(III)) excitation spectra, circularly polarized luminescence, and vibrational circular dichroism. It has been revealed that the dodecahedral eight coordinate DD-8-M-Ln complexes in crystals are equilibrated between the diastereoselectively formed square antiprism eight coordinate SAPR-8-M-Ln and [Ln((+)-hfbc)(3)] in EtOH and CH(3) CN solutions or between the SAPR-8-M-Ln and DD-D(2d) (mmmm)-8-M-Ln complexes in CHCl(3) solution. The observed CD couplets are found to reflect the exciton CD couplets which are useful to determine the four-bladed SAPR-(llll) absolute configuration around the lanthanide(III) ion.

Axially chiral 1,1'-bicarbazolyls with near-ultraviolet circularly polarized luminescence.

The facile synthesis and chiroptical properties of a new family of circularly polarized luminescence (CPL) materials, axially chiral 1,1'-bicarbazolyls (BiCz), are reported. The BiCz derivatives emitted intense near-ultraviolet photoluminescence, with a peak at ∼380 nm. The BiCz enantiomers showed mirror-image circular dichroism and CPL, with glum values on the order of 10-4 in solution.

Aggregation-induced chirality amplification of optically active fluorescent polyurethane and a cyclic dimer in the ground and excited states.

Optically active linear polyurethane and a cyclic dimer were synthesized from 2,7-diisocyanatofluorene and 2,2'-dihydroxy-1,1'-binaphthyl. The circular dichroism (CD) spectral intensity of the polymer was amplified at a higher concentration through aggregate formation, while circularly polarized light (CPL) emission was not enhanced. The cyclic dimer's CPL emission was largely amplified (glum 1.1 × 10-2) due to intermolecular excimer formation through aggregation, while the CD intensity was not affected.

Chiral superstructures of insulin amyloid fibrils.

Hydrodynamic forces are capable of inducing structural order in dispersed solid phases, and of causing symmetry-breaking when chiral crystals precipitate from an achiral liquid phase. Until it was observed upon vortex-assisted fibrillation of insulin, such behavior had been thought to be confined to few unbiological systems. In this paper we are discussing chiroptical properties of two chiral variants of insulin amyloid, termed +ICD and -ICD, which form during the process of chiral bifurcation in vortexed solutions of aggregating insulin. As conventional measurements of circular dichroism of solid, anisotropic substances are particularly vulnerable to overlapping influences of linear birefringence and linear dichroism, we have employed complementary tools including dedicated universal chiroptical spectrophotometer to rule out such artifacts. We propose that the strong chiroptical properties of +ICD and -ICD insulin fibrils are an aspect of genuine superstructural chirality of amyloid fibrils and of powerful excitonic couplings taking place within them. A comparison of thioflavin T complexes with fibrils formed by insulin and polyglutamic acid suggests that the extrinsic Cotton effect stemming from the level of single twisted dye molecules is weaker, although diagnostically useful, and cannot account for the overall magnitude of ICD of the dye bound to ±ICD insulin amyloid.

Finding and characterizing a catalytic antibody light chain, H34, capable of degrading the PD-1 molecule.

Programmed cell death 1 (PD-1) is an immune checkpoint molecule regulating T-cell function. Preventing PD-1 binding to its ligand PD-L1 has emerged as an important tool in immunotherapy. Here, we describe a unique human catalytic antibody light chain, H34, which mediates enzymatic degradation of human PD-1 peptides and recombinant human PD-1 protein and thus functions to prevent the binding of PD-1 with PD-L1. H34 degraded one half of the PD-1 molecules within about 6 h under the experimental conditions. Investigating the acquisition of the catalytic function by H34, which belongs to subgroup I and lacks a Pro95 residue in CDR-3, revealed the importance of this sequence, as a Pro95-reconstituted mutant (H34-Pro95(+)) exhibited very little catalytic activity to cleave PD-1. Interestingly, EDTA inhibited the catalytic activity of H34, which could work as a metallo-protease. Zn2+ or Co2+ ions may work as a cofactor. It is meaningfull that H34 was obtained from the human antibody gene taken from a healthy volunteer, suggesting that we potentially have such unique molecules in our body.