Tris(benzocyclobutadieno)triphenylene and its lower biphenylene homologues by palladium-catalyzed cyclizations of 2,3-didehydrobiphenylene

[reaction: see text] The Pd-catalyzed cycloaddition of didehydrobiphenylenes 2a,b, generated from the corresponding 3-(trimethylsilyl)-2-biphenylenyl triflates with fluoride, furnishes the C3-symmetric trimers 1a,b in which the embedded triphenylene unit is distorted to increase the aromaticity of the central benzene ring. Cocyclization of 2a,b with dimethyl acetylenedicarboxylate provides the phenanthrene- and naphthalenecarboxylic ester analogues, depending on the catalyst used.     

Cobalt-mediated synthesis of angular [4]phenylene: structural characterization of a metallacyclopentadiene(alkyne) intermediate and its thermal and photochemical conversion

[reaction: see text] The first X-ray crystal structure of a mononuclear metallacyclopentadiene(alkyne) complex has been obtained. This type of metallacycle is believed to be the key intermediate in the cobalt-mediated [2 + 2 + 2]cycloaddition of alkynes. Thermal treatment leads to the generation of angular [4]phenylene, the X-ray structural details of which are described. Under photochemical conditions, the cobaltacycle isomerizes to a highly strained (cyclobutadieno)dibenzocyclooctatrienyne complex.     

Electronic correlations at the α-γ structural phase transition in paramagnetic iron

We compute the equilibrium crystal structure and phase stability of iron at the α(bcc)-γ(fcc) phase transition as a function of temperature, by employing a combination of ab initio methods for calculating electronic band structures and dynamical mean-field theory. The magnetic correlation energy is found to be an essential driving force behind the α-γ structural phase transition in paramagnetic iron.     

Exploring the Potential of Fulvalene Dimetals as Platforms for Molecular Solar Thermal Energy Storage: Computations,Syntheses, Structures,Kinetics, and Catalysis

A study of the scope and limitations of varying the ligand framework around the dinuclear core of FvRu₂ in its function as a molecular solar thermal energy storage framework is presented. It includes DFT calculations probing the effect of substituents, other metals, and CO exchange for other ligands on ΔH_storage. Experimentally, the system is shown to be robust in as much as it tolerates a number of variations, except for the identity of the metal and certain substitution patterns. Failures include 1,1′,3,3′‐tetra‐tert‐butyl ( 4 ), 1,2,2′,3′‐tetraphenyl ( 9 ), diiron ( 28 ), diosmium ( 24 ), mixed iron‐ruthenium ( 27 ), dimolybdenum ( 29 ), and ditungsten ( 30 ) derivatives. An extensive screen of potential catalysts for the thermal reversal identified AgNO₃–SiO₂ as a good candidate, although catalyst decomposition remains a challenge.     

Isotherms of phospholipid monolayers measured by a pendant drop technique

The Axisymmetric Drop Shape Analysis (ADSA) has been used to study the surface pressure/area isotherms of insoluble surfactant monolayers. The continuous measurement of surface tension as a function of surface area by increasing and decreasing the drop volume allows to investigate the phase transitions in monolayers. The isotherms of two phospholipids, dipalmitoyl phosphatidyl choline (DPPC) and dimyristoyl phosphatidyl ethanolamine (DMPE), show good agreement with those measured by using a conventional Langmuir-Blodgett film balance, except in the coexistence region. The observed disagreements are discussed in terms of differences in compression rate, curvature of the surface and effect of impurities. Evidence of possible geometric effects on monolayer domain formation and growth is given on the basis of BAM images.Due to the small total surface area, the ADSA technique provides advantages as regards homogeneity of temperature, surface pressure, surface concentration and the symmetry of area changes.