Mesogenic and magnetic behavior in cobalt(II) and iron(II) compounds with long alkyl chains

Abstract  

Metal complexes with long alkyl chains [Co(C16-terpy)₃](BF₄)₂ (1), [Fe(C16-terpy)₂](BF₄)₂ (2), [Co(C16-terpy)₂](BPh₄)₂ (3), [Co(C14-terpy)₂](BF₄)₂ (4), and [Fe(C12C10C5-terpy)₂](BF₄)₂ (5) were synthesized and their physical properties characterized, where C16-terpy, C14-terpy, and C12C10C5-terpy are 4′-hexadecyloxy-2,2′:6′,2′′-terpyridine, 4′-tetradecyloxy-2,2′:6′,2′′-terpyridine, and 4′-5′′′-decyl-1′′′-heptadecyloxy-2,2′:6′,2″-terpyridine, respectively. Complexes 1, 2, and 5 exhibited liquid–crystal properties in the temperature ranges of 371–528 K and 466–556 K, and 88–523 K, respectively. Variable-temperature magnetic susceptibility measurements revealed that the Co(II) complexes 1 and 4 exhibited unique spin transitions (T _1/2↓ = 217 K and T _1/2↑ = 260 K for 1 and T _1/2↓ = 250 K and T _1/2↑ = 307 K for 4), so-called ‘reverse spin transition,’ induced by structural phase transitions. Complex 3 exhibited gradual spin-crossover behavior (T _1/2 = 160 K.), and complex 5 exhibited spin transitions (T _1/2↑ = 288 K and T _1/2↓ = 284 K) at the liquid crystal transition temperature. Compounds with multifunction, i.e., magnetic and liquid–crystal properties, are important in the development of molecular materials.     

Flame structure and stabilization of lean-premixed sprays in a counterflow with low-volatility fuel

An experimental study was performed on the combustion of lean-premixed spays in a counterflow. n-Decane was used as a liquid fuel with low volatility. The flame structure and stabilization were discussed based on the flame-spread mechanism of a droplet array with a low-volatility fuel. The spray flame consisted of a blue region and a yellow luminous region. The flame spread among droplets and group-flame formation through the droplet interaction were observed on the premixed spray side, while envelope flames were also observed on the opposing airflow side. The blue-flame region consisted of premixed flames propagating in the mixture layer around each droplet, the envelope diffusion flames around each droplet, the lower parts of the group diffusion flame surrounding each droplet cluster, and the envelope flame around droplets passing through the group flame. The flame was stabilized within a specific range of the mean droplet diameter via a balance between the droplet velocity and the flame-spread rate of the premixed spray.     

The Relationship between Age and Change in Physical Functions after Exercise Intervention. Trainability of Japanese Community-Dwelling Older Elderly

The purposes of this study were to evaluate the relationship between age and changes in physical measurements after exercise intervention and to investigate the trainability of the older elderly. Two hundred seventy-six community-dwelling people aged 60 years and older practiced exercise intervention for 3 months. The measurements of physical functions were one-legged standing with eyes open and closed (OLS-O, OLS-C), functional reach test (FR), timed up and go test (TUG), maximum walking velocity, flexibility, and muscle strength. We evaluated the associations between age and the changes in these physical measurements. All measurements except for OLS-C significantly improved after intervention. The magnitude of the changes in hand-grip strength and FR after the intervention showed weak negative correlations with the subject''s age, but other measurements showed no correlations. In addition, there were no differences between younger elderly persons and older elderly persons with regard to changes in any measurements. These results suggested that the exercise intervention we applied could improve physical fitness in community-dwelling older people, regardless of their age. The older elderly were comparable to the younger elderly in trainability to improve physical fitness.     

Palladium on carbon‐catalyzed direct C—H arylation polycondensation of 3,4‐ethylenedioxythiophene with various dibromoarenes

We have demonstrated a direct arylation polycondensation of 3,4‐ethylenedioxythiophene with 2,7‐dibromo‐9,9‐dioctylfluorene using palladium on carbon (Pd/C) as a catalyst. Pd/C is a low‐cost solid‐supported palladium catalyst, giving one of the effective catalytic systems for direct arylation. The Pd/C‐catalyzed direct arylation polycondensation with acetic acid/potassium carbonate in N,N‐dimethylacetamide furnished a high molecular weight π‐conjugated alternating copolymer of EDOT‐fluorene (M_n = 89,300, M_w/M_n = 3.27) in high yield. The polycondensation of EDOT with various dibromoarenes was also achieved, giving EDOT‐carbazole, EDOT‐dialylamine, and EDOT‐bithiophene polymers. Optical and electrochemical properties of the polymers were also discussed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1183–1188     

Observation of a Metastable P‐Heterocyclic Radical by Muonium Addition to a 1,3‐Diphosphacyclobutane‐2,4‐diyl

A 1,3‐diphosphacyclobutane‐2,4‐diyl contains a unique unsaturated cyclic unit, and the presence of radical‐type centers have been expected as a source of functionality. This study demonstrates that the P‐heterocyclic singlet biradical captures muonium (Mu=[μ⁺e^?]), the light isotope of a hydrogen radical, to generate an observable P‐heterocyclic paramagnetic species. Investigation of a powder sample of 2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1‐t‐butyl‐3‐benzyl‐1,3‐diphosphacyclobutane‐2,4‐diyl using muon (avoided) level‐crossing resonance (μLCR) spectroscopy revealed that muonium adds to the cyclic P₂C₂ unit. The muon hyperfine coupling constant (A_μ) indicated that the phosphorus atom bearing the t‐butyl group trapped muonium to provide a metastable P‐heterocyclic radical involving the ylidic MuP(<)=C moiety. The observed regioselective muonium addition correlates the canonical formula of 1,3‐diphosphacyclobutane‐2,4‐diyl.     

Structural evolution of glutathionate-protected gold clusters studied by means of 197 Au Mössbauer spectroscopy

¹⁹⁷Au Mössbauer spectra of a series of glutathionate-protected gold clusters, Au _n (SG) _m , with n = 10 ? ~55, were re-analyzed to understand the structure evolution behavior. The numbers of gold atoms coordinated by different numbers (0, 1, and 2) of the GS ligands were successfully determined by assuming individual isomer shifts and quadrupole splittings for the three sites in Au₂₅(SG)₁₈ (Tsukuda et al., Chem Lett 40:1292, 2011). The analysis revealed the drastic structural evolution of Au _n (SG) _m in the range of n = 10 ? ~55. In Au₁₀(SG)₁₀, all the gold atoms are bonded to GS ligands, indicating –Au–S(G)– cyclic structures. A catenane structure was proposed for Au₁₀(SG)₁₀. At n = 25, a single Au atom without the GS ligation appeared, consistent with the formation of an icosahedral Au₁₃ core protected by six staples, –S(G)–[Au–S(G)–]₂. At n = 39, it is considered that Au₃₉(SG)₂₄ has a similar structure to that of Au₃₈(SC₂H₄Ph)₂₄ with face-fused bi-icosahedral Au₂₃ core.