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Macrocycle engineering is a key topic in supramolecular chemistry. When synthesizing a ring, one can obtain either complex mixtures of macrocycles of different sizes or a single ring if a template is utilized. Here, we unite these approaches along with post‐synthetic modifications to transform a single tether into multiple rings—up to five per tether. The macrocycles contain two bridged phenylpyridine ligands that are connected through a Pt atom, which defines the rings' shape, size, and host activity. All rings undergo redox reactions (between PtII and PtIV) that allow for large conformational changes. Their reactivity, together with their host performance, is a convenient way to control the capture and release of guests, to mediate ring transformations, and to control pseudorotaxane‐to‐pseudorotaxane conversions. This novel approach could serve to assemble other libraries of small ring molecules, create cyclic polymers bridged by responsive‐at‐metal nodes, and produce processable mechanically interlocked molecules. [ABSTRACT FROM AUTHOR]

A computational investigation about the Lewis acid-base adducts between bases [Cp.sub.2]M[H.sub.2] (M = Mo, W) and acids B[X.sub.3] (X = F, Cl) and [Al([CH.sub.3].sub.3] is presented. Density functional methods based on pure and hybrid correlation-exchange functionals and relativistic corrections based on the zero order relativistic approximation (ZORA) have been applied. A comparison with experimental data has been addressed to give insights about the nature of the acid-base interaction with the aim to evaluate the role of the transition metal in charge donation toward the acid centre. In this respect, the likelihood of proposed criteria for recognizing the presence of transition-metal direct charge donation has been discussed. Key words: metallocenes, Lewis basicity, density functional theory (DFT), atoms in molecules (AIM), zero order relativistic approximation (ZORA). On a effectue une etude theorique des adduits acide-base de Lewis entre les bases [Cp.sub.2]M[H.sub.2] (M = Mo, W) et les acides B[X.sub.3] (X = F, Cl) et [Al([CH.sub.3].sub.3]. On a utilise les methodes de la fonctionnelle de la densite en faisant appel a des fonctionnelles de correlation-echange pures ainsi qu'hybrides et on a applique des corrections relativistes basees sur l'approximation relativiste d'ordre zero (AROZ). Une comparaison avec les donnees experimentales a ete realisee afin d'obtenir des informations sur la nature de l'interaction acide-base qui permettraient d'evaluer le role du metal de transition dans le transfert de charge vers le centre acide. Dans cette optique, on discute du potentiel d'utilite des criteres proposes pour reconnay tre la presence d'un transfert de charge direct de la part du metal de transition. Mots-cles : metallocenes, basicite de Lewis, theorie de la fonctionnelle de la densite (TFD), atomes dans une molecule << AIM >>, approximation relativiste d'ordre zero (AROZ). [Traduit par la Redaction], Introduction The acid-base adduct between bis(cyclopentadienyl)dihydridotungsten ([Cp.sub.2]W[H.sub.2]) and B[F.sub.3] was firstly communicated by Shriver (1) in 1963. It represented one of the first (and representative) examples of Lewis base behaviour [...]

The synthesis and the full spectroscopic characterization (FT-IR, FT- Raman, [sup.31]P CP MAS NMR) of trans-bis[O-ethyl-phenylphosphonodithioato][Ni.sup.II] (3) are reported. On the basis of hybrid-Density Functional Theory (DFT) calculations and Extended Huckel Theory (EHT) calculations, performed on the simpler trans-bis[O-methyl-phenylphosphonodithioato][Ni.sup.II] (2) model complex, the electronic structures of phosphonodithioato complexes in their ground states are fully described, and in particular the vibrational features are deeply analyzed, allowing an unprecedented insight into the vibrational features of trans-bis-O-methyl-phenylphosphono- and trans-bis(isopropylamidophosphono)-dithioato complexes of nickel(II), palladium(II), and platinum(II). Key words: phosphonodithioato complexes, IR, Raman, DFT calculation.

The syntheses of the first examples of selenoparabanic acid derivatives (dialkylimidazolidine-2-selone-4,5-dione, [3e.sup.R], R = Me, Et, Bu) are presented along with the X-ray crystal structure determination of 3[e.sup.Et]. To gain an insight in the properties of parabanic acid derivatives on the basis of their electronic structures, we report the results of comparative hybrid-DFT calculations performed on parabanic, thioparabanic, and selenoparabanic acids ([3a.sup.H], [3b.sup.H], and [3e.sup.H] and on their N,N'-dimethyl derivatives [3a.sup.Me], [3b.sup.Me], and [3e.sup.Me]. Calculations show that the different nature of the frontier orbitals of [3a.sup.R] compared to those of [3b.sup.R] and [3e.sup.R], might account for the different reactivities of these compounds. Moreover, the weak donor character of [3b.sup.R] and [3e.sup.R] towards molecular di-iodine, estimated by FT-Raman measurements is in agreement with the calculated NBO-charge distribution. Key words: selenation, selenoparabanic derivatives, crystal structure, DFT calculations.

Molecular dynamics simulations at atomistic level have been performed on a metal-porphyrazine complex. Starting from an isotropic state, the system was cooled until transition from isotropic to columnar phase was observed; no nematic phase was encountered. Many tools were utilized to follow the system evolution: order parameter, g(r), g∥(r∥), gc(r∥), g⊥(r⊥), g2(r), also density and energy changes. Very long runs were required to get reliable results, times greater than 40 ns of simulation. The structure of columnar phase was analyzed and the organization of molecules in the columns was investigated, along with the role of conformation of side chains. We found that in columnar phase the molecules are tilted versus the column axis and the conformation of side chains changes during the phase transition to allow this kind of organization; moreover the direction of columns axes is different from that of the director. [ABSTRACT FROM AUTHOR]

A family of molecular heptacadmium carboxylate clusters templated inside [3+3] Schiff base macrocycles is isolated and analyzed by variable temperature solution and solid-state NMR spectroscopy, single-crystal X-ray diffraction (SCXRD), and density functional theory (DFT) calculations. The studies have helped in understanding the host-guest and dynamics properties of a new family of metallocavitands and have helped in designing new supramolecular catalysts and materials.

The form of 8-hydroxyquinoline in different solvents is examined by using spectroscopic and computational methods. The results have shown that 8-hydroxyquinoline has displayed a clear preference for the cis conformation, but a small fraction of the trans conformation is present in water solutions.

The synthesis, characterization and photoreactivity of a series of new heteroaryl imines form the coupling between 2-benzothienyldiphenylmethyliminophosphorane and heterocyclic aldehydes are described. The reaction at 60 degree Celsius gave the formation of only the trans isomer while at high temperature cis isomer was obtained and only the cis isomers showed a photochemical reactivity to give corresponding condensed pyridine derivative.

Nonrelativistic and relativistic time-dependent density functional calculations are performed on the excited states of the [M(H2timdt)(sub 2)] (M = Ni, Pd, Pt) compounds. In all members of the series, the excited state at the lowest energy corresponds to a HOMO -> LUMO excitation and indicates that a large number of the transitions have an intraligand character.

Research has been conducted on 2,3-epoxy alcohols. The authors describe their study of the role of metal ions in regioselective opening of these alcohols carried out via hybrid density functional theory method.

Density functional theory and time-dependent density functional theory were applied to describe the ground and excited states and the spectral characteristics of the meridianal and facial isomers of aluminum tris(quinolin-8-oclate) (Alq3). Experimental meridinal Alq3 absorption band locations were well reproduced by the computations, which allowed easy assignment of the absorption bands.

The results of a systematic density functional study, carried out using a self-consistent hybrid approach including exact exchange contribution, on the all monocarbonyls of first-row transition metals, are reported. Geometries, harmonic wave numbers, and binding energies, obtained using both standard generalized gradient corrected and hybrid functionals, are compared with previous published theoretical data and the available experimental findings. It is shown that hybrid functionals give results close to highly correlated post Hartree–Fock approaches and which are sensibly different from those obtained by standard local, even gradient corrected, methods. A nice agreement has been also found between theoretical and experimental binding energies. A natural bond orbital analysis confirms the role of the π interaction in the metal-carbonyl bond and gives an explanation to the preference for bent structures found in chromium and copper monocarbonyls. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Density functional calculations with large basis sets have been performed for nine conformers of neutral glycine. The results obtained by standard, even gradient corrected functionals are significantly different from the best post-Hartree–Fock computations and the available experimental data. Inclusion of some Hartree–Fock exchange significantly improves matters, thus providing a promising protocol for the study of noncovalent interactions in biomolecules. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations on the geometry and bonding energy of the X - - - I intermolecular interaction of CF3I and (CH3)(sub n)X and (CH3)(sub n)XO are reported. All the adducts with the oxides as donors show a weaker interaction with CF3I than the relative donor without oxygen except the CF3I - - - ON(CH3) adduct, which has a stronger interaction.

The Mn (OESPz) complex reacts with perfluorodecalin or 1,2-difluorobenzene affording the fluromanganese (III) (ethylsulfanyl) porphyrazinato complex and defluorinated organic products. The preliminary results of this investigation concern the use of Mn (OESPz) in the chemical and electrochemical reductive defluorination of perfluorodeclain.