Second-order Møller−Plesset (MP2) calculations (using the approximate resolution of the identity, RI-MP2) in the TZVPP basis are performed to study the interaction of molecular hydrogen with the aromatic systems C6H5X (X = H, F, OH, NH2, CH3, and CN), C10H8 (naphthalene and azulene), C14H10 (anthracene), C24H12 (coronene), p-C6H4(COOH)2 (terephthalic acid), and p-C6H4(COOLi)2 (dilithium terephthalate). Various adsorption positions are studied for C6H5F. The most favorable configuration places H2 above the aromatic plane with its axis pointing toward the middle of the ring. The electronic (van der Waals) interaction energy for the differently substituted benzenes correlates with the ability of the substituents to enrich the aromatic system electronically. The largest interaction energy (among the singly substituted benzenes) is found for aniline (4.5 kJ mol-1). Enlarging the aromatic system increases the interaction energy; the value for coronene amounts to 5.4 kJ mol-1. Extending the basis set and including terms linear in the interelectronic distances increases the interaction energy by about 1 kJ mol-1 relative to that of the TZVPP basis, whereas the inclusion of higher excitations by coupled-cluster calculations (including all single and double excitations with a perturbative estimate of triples, CCSD(T)) decreases the interaction energy by about the same amount.

Organic electron donors are of importance for a number of applications. However, the factors that are essential for a directed design of compounds with desired reduction power are not clear. Here, we analyze these factors in detail. The intrinsic reduction power, which neglects the environment, has to be separated from extrinsic (e.g., solvent) effects. This power could be quantified by the gas-phase ionization energy. The experimentally obtained redox potentials in solution and the calculated ionization energies in a solvent (modeled with the conductor-like screening model (COSMO)) include both intrinsic and extrinsic factors. An increase in the conjugated π-system of organic electron donors leads to an increase in the intrinsic reduction power, but also decreases the solvent stabilization. Hence, intrinsic and extrinsic effects compete against each other; generally the extrinsic effects dominate. We suggest a simple relationship between the redox potential in solution and the gas-phase ionization energy and the volume of an organic electron donor. We finally arrive at formulas that allow for an estimate of the (gas-phase) ionization energy of an electron donor or the (gas-phase) electron affinity of an electron acceptor from the measured redox potentials in solution. The formulas could be used for neutral organic molecules with no or only small static dipole moment and relatively uniform charge distribution after oxidation/reduction.

Keywords: Electron donor ligands / Cobalt / Aluminum / N ligandsHerein we report on the synthesis and properties of a new electron donor featuring an aromatic system to which four guanidino groups are attached, namely, 1,4,5,8-tetrakis(tetramethylguanidino)naphthalene (ttmgn). The molecule is a double proton sponge with an asymmetric N-H···N bridge being formed in the protonated form. Oxidation is followed electrochemically, and two oxidation waves at E 1/2 (CH 3 CN) = -0.25 and +0.50 V vs. SCE are observed. Chemical oxidation with I 2 yields ttmgn(I 3 ) 2 , in which the I 3 units interact with the ttmgn 2+ cations through I···C contacts. Reaction with an excess amount of Br 2 leads to removal of four electrons from the aromatic system and formation of the salt (ttmgn)-Br 4 with a chair-type conformation of the C 10 core. The binuclear Al alkyl complex [(ttmgn)(AlMe 2 ) 2 ][BPh 4 ] 2 can be pre- [a] Anorganisch- Synthesis and CharacterisationThe synthesis of 3 turned out to be much more difficult than that of 2. Nevertheless, its preparation was achieved www.eurjic.org

The relative energies of a multitude of low-lying electronic states of Fe 2 S 2 Ϫ/0/ϩ/2ϩ have been determined by complete active space self-consistent-field ͑CASSCF͒ calculations. For selected states dynamical correlation has been included by the multireference configuration interaction method ͑MRCI͒ and the structures of some high-spin states have been optimized by CASSCF/ MRCI. Comparison is made with structures obtained by density functional calculations. In all oxidation states of Fe 2 S 2 the numerous states are assigned to spin ladders. The ground states of Fe 2 S 2 Ϫ/0/ϩ/2ϩ are 10 A g , 1 A g , 2 B 1u and 1 A g , respectively. The total splittings of the lowest-energy spin ladders of Fe 2 S 2 , Fe 2 S 2 Ϫ , and Fe 2 S 2 ϩ are about 0.17, 0.18, and 0.35 eV, respectively. The spin ladders of Fe 2 S 2 qualitatively reflect the picture of Heisenberg spin coupling. Some of the spin ladders of Fe 2 S 2 ϩ show the picture of combined Heisenberg coupling and double exchange. The calculated adiabatic electron affinity of Fe 2 S 2 is 1.1 eV ͑observed 2.1 eV͒. Our estimate of the ionization energy of Fe 2 S 2 is 7.9Ϯ0.5 eV. An interpretation of the observed photoelectron spectrum of Fe 2 S 2 Ϫ is given.

The Ti dimer is fairly weakly bound, but highly reactive, and completely cleaves the strong N2 triple bond in just one step without activation energy (see scheme; Ti red, N blue). In contrast, a Ti atom in its ground electronic state does not react with N2.

The structures and relative energies of different isomers and different electronic states of Fe 2 S 2 À/0/+/2+ , Fe 2 S À/0/+/2+ , Fe 2 À/0/+/2+ , FeS 2 À/0/+ , FeS À/0/+ , Fe À/0/+/2+ , S 2 À/0 , and S À/0 have been determined by density functional theory (DFT) using the B3LYP functional. Comparison is made with CASSCF/MRCI results for Fe 2 , FeS and Fe 2 S 2 . The broken symmetry approach provides a realistic description of the Heisenberg spin coupling in Fe 2 S 2 0/+ . The mean absolute deviations of bond dissociation energies, ionization energies and adiabatic electron affinities from available experimental results are 0.18, 0.31 and 0.20 eV, respectively. 5234

Several new mono-and dinuclear complexes of Co II and Ni II with chelating guanidine ligands were synthesized. The molecular structures for most of the complexes in the crystalline state were derived from single-crystal X-ray diffraction, and some characteristic structural details are discussed. The molecular magnetism was further studied by superconducting

In this work we report on the syntheses and properties of the first transition metal complexes of the proton sponge 1,8-bis(N,N,NЈ,NЈ-tetramethylguanidino)naphthalene (btmgn show some interesting details. X-ray crystallographic studies reveal that the naphthyl aromatic systems in both complexes are not planar, the metal atoms reside above the "best-plane" of the naphthyl systems and the compounds adopt a chiral conformation in the crystalline phase.