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Strigolactones (SLs) are plant apocarotenoids with diverse roles and structures. Canonical SLs, widespread and characterized by structural variations in their tricyclic lactone (ABC-ring), are classified into two types based on C-ring configurations. The steric C-ring configuration emerges during the BC-ring closure, downstream of the biosyn-thetic intermediate, carlactonoic acid (CLA). Most plants produce either type of canonical SLs stereoselectively, e.g., tomato (Solanum lycopersicum) yields orobanchol with an α-oriented C-ring. The mechanisms driving SL structural diversification are partially understood, with limited insight into functional implications. Furthermore, the exact molecular mechanism for the stereoselective BC-ring closure reaction is yet to be known. We identified an enzyme, the stereoselective BC-ring-forming factor (SRF), from the dirigent protein (DIR) family, specifically the DIR-f subfamily, whose biochemical function had not been characterized, making it a key enzyme in stereoselective canonical SL biosynthesis with the α-oriented C-ring. We first confirm the precise catalytic function of the tomato cytochrome P450 SlCYP722C, previously shown to be involved in orobanchol biosynthesis [T. Wakabayashi et al., Sci. Adv. 5, eaax9067 (2019)], to convert CLA to 18-oxocarlactonoic acid. We then show that SRF catalyzes the stereoselective BC-ring closure reaction of 18-oxocarlactonoic acid, forming orobanchol. Our methodology combines experimental and computational techniques, including SRF structure prediction and conducting molecular dynamics simulations, suggesting a catalytic mechanism based on the conrotatory 4π-electrocyclic reaction for the stereoselective BC-ring formation in orobanchol. This study sheds light on the molecular basis of how plants produce SLs with specific stereochemistry in a controlled manner. [ABSTRACT FROM AUTHOR]

Redox-flow batteries (RFBs) are promising electrochemical energy storage devices to load-level intermittent power from renewable energy. In particular, aqueous RFBs using aqueous electrolytes possess several advantages over nonaqueous ones, such as low fabrication cost, nontoxicity, safety, and environmental benignity. Therefore, developing high-performance, abundant, less-expensive iron-based catholytes for aqueous RFBs is essential toward their wide deployment in a power grid. In this Perspective, we summarize the recent progress of iron-based catholytes for aqueous RFBs. We emphasize that iron-based catholytes possess widely ranged redox potentials (-1.0 to 1.5 V vs standard hydrogen electrodes) and solubility in water (0.2-4.0 mol L-1), thereby providing a wide range of cell performance. The molecular design, such as ligand functionalization, counter ion mixing, and asymmetrization, allows for rationally improving solubility, redox potential, and energy density. Furthermore, we demonstrate a simple evaluation method of the redox potential of iron-based catholytes using the calculated energy levels of the lowest unoccupied molecular orbital of ligand molecules. Finally, we rationalize the design strategy of iron-based catholytes for advanced aqueous RFBs. [ABSTRACT FROM AUTHOR]

One of the most attractive research in the field of molecular solids is multifunctional molecular magnets coupled with spin, charge and photon, and singlemolecular magnet/single-chain magnet toward spintronics. In this chapter, we focus on the molecular magnetism and its related light-induced phase transitions from the viewpoint of Mössbauer spectroscopy. In the Sect. 6.1, the outline of this chapter is described. In the Sect. 6.2, static and dynamic spin crossover phenomena between the high-spin and low-spin states, and the spin frustration system induced by dynamic spin crossover phenomena for [MnIIFeIII(C2O3S)3] complex are described. In the Sect. 6.3, metal complexes showing charge transfer phase transitions such as Prussian blue analogous complexes and [MnIIFeIII(C2O3S)3] complexes and their photoinduced phase transitions are described. In the Sect. 6.4, various kinds of molecular magnets including single molecular chain magnets are described. [ABSTRACT FROM AUTHOR]

Four Fe(III) spin-crossover (SCO) compounds, [Fe(HL1)2](HCl4TPA) (1-Cl), [Fe(HL1)2 ](HBr4TPA) (1-Br), [Fe(HL2)2](HCl4TPA) (2-Cl), and [Fe(HL2)2](HBr4TPA) (2-Br) (HL1 = 4-chloro-2-nitro-6-(1-(2-(pyridine-2-yl)hydrazono)ethyl)phenolate; HL2 = 4-bromo-2-nitro-6-(1-(2-(pyridine-2-yl)hydrazono)ethyl)phenolate; HCl4TPA = 2,3,5,6-tetrachloro-4-carboxybenzoate; and HBr4TPA = 2,3,5,6-tetrabromo-4-carboxybenzoate), were synthesized to investigate the halogen substituent change effect in salicylaldehyde 2-pyridyl hydrazone-type ligands and dicarboxylic acids in SCO complexes to the spin-transition temperature. Crystal structure analyses showed that these compounds were isostructural. In addition, a one-dimensional hydrogen-bonded column was formed by the dicarboxylic acid anion and weak hydrogen bonds between the Fe(III) complexes. From Mössbauer spectroscopy and magnetic property measurements, these compounds were confirmed to exhibit gradual SCO. The spin-transition temperature can be shifted by changing the halogen substituent in the salicylaldehyde 2-pyridyl hydrazone-type ligands and dicarboxylic acids without changing the molecular arrangement in the crystal packing. [ABSTRACT FROM AUTHOR]

The spin-crossover (SCO) phenomenon between a high-spin and a low-spin state has attracted much attention in the field of materials science. Among the various kinds of SCO complexes, the triazole-bridged iron(II) polymeric chain system, [Fe(II)(R-trz)3]X2.xH2O (where trz is triazole and X is the anion), exhibiting the SCO phenomenon with thermal hysteresis around room temperature, has been extensively studied from the viewpoint of molecular memory and molecular devices. In connection with this system, we have controlled the SCO phenomenon according to the characteristic properties of counter ions. In the case of X being CnH2n+1SO3-, the spin transition temperature (T1/2) increases with increasing the length (n) of the alkyl chain of the counter ion and saturates above n = 5, which is attributed to the increase in the intermolecular interaction of the alkyl chains of CnH2n+1SO3 -, called the fastener effect. The hysteresis width of T1/2 decreases with increasing n, showing the even-odd, also known as parity, effect. In the cases where X is toluenesulfonate (tos: CH3C6H4SO3 -) and aminobenzenesulfonate (abs: NH2C6H4SO3 -), T1/2 and its hysteresis width vary drastically with the structural isomerism (ortho-, metha-, and para-substitution) of counter ions, which implies the possibility of photoinduced spin transition by means of the photoisomerization of counter ions. From this strategy, we have synthesized [Fe(II)(NH2-trz)3](SP150)2.2H2O (SP150 = N-alkylsulfonated spiropyran) and investigated the SCO phenomenon. Moreover, we have developed [Fe(II)(R-trz)3]@Nafion films exhibiting spin transition around room temperature, where the Nafion membrane behaves as a counter anion as well as a transparent substrate, and investigated the photogenerated high-spin state below 35 K. The lifetime of the photogenerated high-spin state strongly depends on the intensity of irradiated light. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of a range of new iron(III) bis-tridentate Schiff base complexes are described with emphasis on how intermolecular structural interactions influence spin states and spin crossover (SCO) in these d5 materials. Three pairs of complexes were investigated. The first pair are the neutral, heteroleptic complexes [Fe(3-OMe-SalEen)(thsa)] 1 and [Fe(3-MeOSalEen)(3-EtOthsa)] 2, where 3-R-HSalEen = (E)-2-(((2-(ethylamino)ethyl)imino)methyl)-6-R-phenol and 3-R-H2thsa = thiosemicarbazone-3-R-salicylaldimine. They display spin transitions above room temperature. However, 2 shows incomplete and gradual change, while SCO in 1 is complete and more abrupt. Lower cooperativity in 2 is ascribed to the lack of p-p interactions, compared to 1. The second pair, cationic species [Fe(3-EtOSalEen)2]NO3 3 and [Fe(3-EtOSalEen)2]Cl 4 differ only in the counter-anion. They show partial SCO above room temperature with 3 displaying a sharp transition at 343 K. Weak hydrogen bonds from cation to Cl- probably lead to weaker cooperativity in 4. The last pair, CsH2O[Fe(3-MeO-thsa)2] 5 and Cs(H2O)2[Fe(5-NO2-thsa)2] 6, are anionic homoleptic chelates that have different substituents on the salicylaldiminate rings of thsa2-. The Cs cations bond to O atoms of water and the ligands, in unusual ways thus forming attractive 1D and 3D networks in 5 and 6, respectively, and 5 remains HS (high spin) at all temperatures while 6 remains LS (low spin). Comparisons are made to other literature examples of Cs salts of [Fe(5-R-thsa)2]- (R = H and Br). [ABSTRACT FROM AUTHOR]

Four Fe(III) spin-crossover (SCO) compounds, [Fe(HL1)2](HCl4TPA) (1-Cl), [Fe(HL1)2](HBr4TPA) (1-Br), [Fe(HL2)2](HCl4TPA) (2-Cl), and [Fe(HL2)2](HBr4TPA) (2-Br) (HL1 = 4-chloro-2-nitro-6-(1-(2-(pyridine-2-yl)hydrazono)ethyl)phenolate; HL2 = 4-bromo-2-nitro-6-(1-(2-(pyridine-2-yl)hydrazono)ethyl)phenolate; HCl4TPA = 2,3,5,6-tetrachloro-4-carboxybenzoate; and HBr4TPA = 2,3,5,6-tetrabromo-4-carboxybenzoate), were synthesized to investigate the halogen substituent change effect in salicylaldehyde 2-pyridyl hydrazone-type ligands and dicarboxylic acids in SCO complexes to the spin-transition temperature. Crystal structure analyses showed that these compounds were isostructural. In addition, a one-dimensional hydrogen-bonded column was formed by the dicarboxylic acid anion and weak hydrogen bonds between the Fe(III) complexes. From Mössbauer spectroscopy and magnetic property measurements, these compounds were confirmed to exhibit gradual SCO. The spin-transition temperature can be shifted by changing the halogen substituent in the salicylaldehyde 2-pyridyl hydrazone-type ligands and dicarboxylic acids without changing the molecular arrangement in the crystal packing. [ABSTRACT FROM AUTHOR]

Root parasitic weeds in Orobanchaceae cause serious damage to worldwide agriculture. Germination of the parasites requires host-derived germination stimulants, such as strigolactones, as indicators of host roots within reach of the parasite's radicles. This unique germination process was focused on to identify metabolic pathways required for germination, and to design a selective control strategy. A metabolomic analysis of germinating seeds of clover broomrape, Orobanche minor, was conducted to identify its distinctive metabolites. Consequently, a galactosylsucrose trisaccharide, planteose (α-d-galactopyranosyl-(1→6)-β-d-fructofuranosyl-(2→1)-α-d-glucopyranoside), was identified as a metabolite that decreased promptly after reception of the germination stimulant. To investigate the importance of planteose metabolism, the effects of several glycosidase inhibitors were examined, and nojirimycin bisulfite (NJ) was found to alter the sugar metabolism and to selectively inhibit the germination of O. minor. Planteose consumption was similar in NJ-treated seeds and non-treated germinating seeds; however, NJ-treated seeds showed lower consumption of sucrose, a possible intermediate of planteose metabolism, resulting in significantly less glucose and fructose. This inhibitory effect was recovered by adding glucose. These results suggest that planteose is a storage carbohydrate required for early stage of germination of O. minor, and NJ inhibits germination by blocking the supply of essential glucose from planteose and sucrose. Additionally, NJ selectively inhibited radicle elongation of germinated seeds of Orobanchaceae plants (Striga hermonthica and Phtheirospermum japonicum). Thus, NJ will be a promising tool to develop specific herbicides to the parasites, especially broomrapes, and to improve our understanding of the molecular mechanisms of this unique germination. [ABSTRACT FROM AUTHOR]

The article discusses polar lipid accumulation profiling in Euglena gracilis, a unicellular eukaryotic flagellate, through in silico approach by LipidBlast, a computer-generated hypothetical tandem mass spectrometry fragment library covering various lipid species. Topics discussed include carbon dioxide fixation in Euglena through pyrenoids, identification of spectrum through liquid chromatography-mass spectrometry analysis and exploration of profiling in anaerobic growth condition.