A Core‐Expanded Subphthalocyanine Analogue with a Significantly Distorted Conjugated Surface and Unprecedented Properties

The introduction of a seven‐membered‐ring unit in the place of a five‐membered‐ring unit in the structure of subphthalocyanine resulted in significant distortion of the bowl‐shaped structure of the conjugated molecule as well as the following unprecedented properties: the preferential formation of the axially fluoro substituted species, the fluttering‐dynamic‐motion‐induced rapid exchange of P and M enantiomers, markedly split Q‐band absorption, and a clear difference in the ring‐current effects arising from the convex and concave surfaces.     

Tricks of Light on Helices: Transformation of Helical Polymers by Photoirradiation

The following polymer structural transitions were achieved using light: preferred‐handed helix formation for poly(9,9‐di‐n‐octylfluoren‐2,7‐diyl), helix racemization (helix–helix transition) for poly(2,7‐bis(4‐t‐butylphenyl)fluoren‐9‐yl acrylate) and poly(2,5‐bis[4‐((S)‐2‐methylbutyloxy)phenyl]styrene), and helix decomposition for poly(2,7‐bis(4‐t‐butylphenyl)‐9‐methylfluoren‐9‐yl acrylate) and poly(2,7‐bis(4‐t‐butylphenyl)fluoren‐9‐ylmethyl methacrylate). Although these types of transitions and chemical transformations have been studied mainly using heat or chemicals as stimuli, light can also cause these structural alterations. In the helix construction and the helix–helix transition, a key transition is a twist‐coplanar conformational change of a biphenyl or an aryl–aryl unit in the side chain or the main chain of the polymer. Furthermore, the helix–helix transition was caused only by light and not by heat. The examples discussed in this review are expected to trigger off a new direction in synthesis and reaction of chiral polymers.     

Regioselective Synthesis of 6‐Prenylpolyhydroxyisoflavone (Wighteone) and Wighteone Hydrate with Hypervalent Iodine

The oxidative rearrangement of 3′‐iodotetraalkoxychalcone with [hydroxyl(tosyloxy)iodo]benzene, followed by cyclization of the resultant acetal gave 6‐iodotrialkoxyisoflavone. The coupling reaction of the isoflavone with 2‐methyl‐3‐butyn‐2‐ol gave 6‐alkynylisoflavone, whose hydrogenation gave wighteone hydrate. Wighteone was synthesized by dehydration of wighteone hydrate.     

Synthesis of Heterocyclic Compounds Using Amidines as Their Ene-1,1-diamine Tautomers,IV: Synthesis of N-Bridged Heterocycles 1,2,3,4-Tetrahydropyrido[1,2-a]pyrimidin-6-ones and Methyl 1,2,3,4-Tetrahydropyrrolo[1,2-a]pyrimidin-7-ylideneacetates

2-Benzyl-1,4,5,6-tetrahydropyrimidines 1 (as ene-1,1-diamine N,C-tautomers) in diglyme reacted with ethyl benzoylacetate at 160 °C in an oil bath to give 1,2,3,4-tetrahydropyrido[1,2-a]pyrimidin-6-ones 3 and with dimethyl acetylenedicarboxylate in methanol at room temperature, leading to methyl 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrimidin-7-ylideneacetates 5, respectively.      

Raman Spectroscopic Study of Rare Earth Chlorides in Alkali Chloride Eutectic Melts

Raman spectra of rare earth (REE: rare earth elements) trichloride (REE = Y, La, Ce, Pr, Sm, Gd, Dy, or Yb) dissolved in alkali chloride eutectic melts (LiCl‐KCl, LiCl‐RbCl, and LiCl‐CsCl) were measured at 793 K. The spectra showed polarized peaks centered around 240–270 cm^–1, which were identified as the totally symmetric stretching vibration (ν₁) of the octahedral REECl₆^3–. The ν₁ frequency increased with the polarizing power of the trivalent REE ions. The change in the ν₁ frequency was found to be larger for lighter lanthanides. This was attributable to the distortion of the O_h symmetry of REECl₆^3–.     

Facile Synthesis of 2,2′‐Dialkylated 4,4′‐Oxybiphenols

2,2′‐Alkyl‐disubstituted 4,4′‐oxybiphenols (4) were prepared in good yields through esterification of 4,4′‐oxybiphenol (1), AlCl₃‐promoted Fries rearrangement, and AlCl₃/NaBH₄‐promoted reduction reaction.     

Charge‐Transfer Solids Using Nucleobases: Supramolecular Architectures Composed of Cytosine and [Ni(dmit)2] Assembled by Multiple Hydrogen Bonds and Heteroatomic Contacts

Protonated species of the nucleobase cytosine (C), namely the monoprotonated CH⁺ and the hemiprotonated CHC⁺, were used to obtain four charge‐transfer complexes of [Ni(dmit)₂] (dmit: 1,3‐dithiole‐2‐thione‐4,5‐dithiolate). Diffusion methods afforded two semiconducting [Ni(dmit)₂]^? salts; (CH)[Ni(dmit)₂](CH₃CN) ( 1 ) and (CHC)[Ni(dmit)₂] ( 2 ). In salt 1 , the [Ni(dmit)₂]^? ions with a S=1/2 spin construct a uniform one‐dimensional array along the molecular long axis, and the significant intermolecular interaction along the face‐to‐face direction results in a spin‐singlet ground state. In contrast, salt 2 exhibits the Mott insulating behavior associated with uniform 1D arrays of [Ni(dmit)₂]^?, which assemble a two‐dimensional layer that is sandwiched between the layers of hydrogen‐bonded CHC⁺ ribbons. Multiple hydrogen bonds between CHC⁺ and [Ni(dmit)₂]^? seem to result in the absence of structural phase transition down to 0.5 K. Electrooxidation of [Ni(dmit)₂]^? afforded the polymorphs of the [Ni(dmit)₂]^0.5? salts, (CHC⁺)[{Ni(dmit)₂}^0.5?]₂ ( 3 and 4 ), which are the first mixed‐valence salts of nucleobase cations with metal complex anions. Similar to 2 , salt 3 contains CHC⁺ ribbons that are sandwiched between the 2D [Ni(dmit)₂]^0.5? layers. In the layer, the [Ni(dmit)₂]^0.5? ions form dimers with a S=1/2 spin and the narrow electronic bandwidth causes a semiconducting behavior. In salt 4 , the CHC⁺ units form an unprecedented corrugated 2D sheet, which is sandwiched between the 2D [Ni(dmit)₂]^0.5? layers that involve ring‐over‐atom and spanning overlaps. In contrast to 3 , salt 4 exhibits metallic behavior down to 1.8 K, associated with a wide bandwidth and a 2D Fermi surface. The ability of hydrogen‐bonded CHC⁺ sheets as a template for the anion radical arrangements is demonstrated.     

Molecular Rotors of Coronene in Charge‐Transfer Solids

Ten types of neutral charge transfer (CT) complexes of coronene (electron donor; D) were obtained with various electron acceptors (A). In addition to the reported 7,7,8,8‐tetracyanoquinodimethane (TCNQ) complex of 1:1 stoichiometry with a DA‐type alternating π column, TCNQ also afforded a 3:1 complex, in which a face‐to‐face dimer of parallel coronenes ( Cor‐A s) is sandwiched between TCNQs to construct a DDA‐type alternating π column flanked by another coronene ( Cor‐B ). Whereas solid‐state ²H NMR spectra of the 1:1 TCNQ complex formed with deuterated coronene confirmed the single in‐plane 6‐fold flipping motion of the coronenes, two unsynchronized motions were confirmed for the 3:1 TCNQ complex, which is consistent with a crystallographic study. Neutral [Ni(mnt)₂] (mnt: maleonitriledithiolate) as an electron acceptor afforded a 5:2 complex with a DDA‐type alternating π column flanked by another coronene, similar to the 3:1 TCNQ complex. The fact that the Cor‐A s in the [Ni(mnt)₂] complex arrange in a non‐parallel fashion must cause the fast in‐plane rotation of Cor‐A relative to that of Cor‐B . This is in sharp contrast to the 3:1 TCNQ complex, in which the dimer of parallel Cor‐A s shows inter‐column interactions with neighboring Cor‐A s. The solid‐state ¹H NMR signal of the [Ni(mnt)₂] complex suddenly broadens at temperatures below approximately 60 K, indicating that the in‐plane rotation of the coronenes undergoes down to approximately 60 K; the rotational rate reaches the gigahertz regime at room temperature. Rotational barriers of these CT complexes, as estimated from variable‐temperature spin–lattice relaxation time (T₁) experiments, are significantly lower than that of pristine coronene. The investigated structure–property relationships indicate that the complexation not only facilitates the molecular rotation of coronenes but also provides a new solid‐state rotor system that involves unsynchronized plural rotators.     

Thermally and Photochemically Induced Charge-Transfer Polymerizations

Polymerizations involving electron donor-acceptor interactions or charge-transfer interactions have been a topic of interest in recent years. Two classes of polymerization are the subjects of major concern in this area. One is a polymerization initiated via charge-transfer interactions involving monomers as one component, which is termed charge-transfer polymerization. The charge-transfer polymerization encompasses both thermal and photochemical processes. The other is an alternating radical copolymerization in which it is thought to be likely that a charge-transfer complex formed between monomer pairs participates as a monomer species in the propagation process of polymerization, the mechanism of which has long been a subject of controversy. Some of the alternating radical copolymerizations are initiated spontaneously via charge-transfer interactions between monomer pairs.     

Fragmentation at sp2 carbon atoms in fragment molecular orbital method

In the fragment molecular orbital (FMO) method, a given molecular system is usually fragmented at sp³ carbon atoms. However, fragmentation at different sites sometimes becomes necessary. Hence, we propose fragmentation at sp² carbon atoms in the FMO method. Projection operators are constructed using sp² local orbitals. To maintain practical accuracy, it is essential to consider the three-body effect. In order to suppress the corresponding increase of computational cost, we propose approximate models considering local trimers. Numerical verification shows that the present models are as accurate as or better than the standard FMO2 method in total energy with fragmentation at sp³ carbon atoms.