Synthesis and Reactivity of Bis(silylene)-Coordinated Calcium and Divalent Lanthanide Complexes.

Divalent lanthanide complexes of Eu (1) and Yb (2) coordinated by a chelating pyridine-based bis(silylene) ligand were isolated and fully characterized. Compared to the EuII complex 1, the YbII complex 2 presents a lower thermal stability, resulting in the activation of one SiII -N bond and formation of an YbIII complex (3), which features a unique silylene-pyridyl-amido ligand. The different thermal stability of 1 and 2 points towards reduction-induced cleavage of one SiII -N bond of the bis(silylene) ligand. Successful isolation of the corresponding redox-inert bis(silylene) CaII complex (5) was achieved at low temperature and thermal decomposition into a CaII complex (4) bearing the same silylene-pyridyl-amido ligand was identified. In this case, the thermolysis reaction proceeds through another, non-redox induced, mechanism. An alternative higher yielding route to 4 was developed through an in situ generated silylene-pyridyl-amine proligand.

TURBOMOLE: Modular program suite for ab initio quantum-chemical and condensed-matter simulations.

TURBOMOLE is a collaborative, multi-national software development project aiming to provide highly efficient and stable computational tools for quantum chemical simulations of molecules, clusters, periodic systems, and solutions. The TURBOMOLE software suite is optimized for widely available, inexpensive, and resource-efficient hardware such as multi-core workstations and small computer clusters. TURBOMOLE specializes in electronic structure methods with outstanding accuracy-cost ratio, such as density functional theory including local hybrids and the random phase approximation (RPA), GW-Bethe-Salpeter methods, second-order Møller-Plesset theory, and explicitly correlated coupled-cluster methods. TURBOMOLE is based on Gaussian basis sets and has been pivotal for the development of many fast and low-scaling algorithms in the past three decades, such as integral-direct methods, fast multipole methods, the resolution-of-the-identity approximation, imaginary frequency integration, Laplace transform, and pair natural orbital methods. This review focuses on recent additions to TURBOMOLE's functionality, including excited-state methods, RPA and Green's function methods, relativistic approaches, high-order molecular properties, solvation effects, and periodic systems. A variety of illustrative applications along with accuracy and timing data are discussed. Moreover, available interfaces to users as well as other software are summarized. TURBOMOLE's current licensing, distribution, and support model are discussed, and an overview of TURBOMOLE's development workflow is provided. Challenges such as communication and outreach, software infrastructure, and funding are highlighted.

Size Matters: From Two-Dimensional AuI -TlI Metallopolymers to Molecular Complexes by Simple Variation of the Steric Demand.

Bis(acetylido) aurates(I) and thallium(I) trifluoromethylsulfonates were used to synthesize AuI -TlI metallopolymers, displaying novel and unusual structural motifs of the metal-metal backbones in the solid state: a discrete molecular cluster, 1D chains of interconnected dimers, tetramers, or dodecamers of Au-Tl units, and a 2D-plane network, consisting of alternating edge-linked (AuTl)6 and (AuTl)4 cycles. The formation of the different architectures was primarily controlled by the steric demand of the acetylide-substituent groups. Thus, the bulkiest 2,6-diisopropylphenyl derivative yielded a molecular cluster [Tl2 Au3 ]. Most compounds showed bright visible photoluminescence with quantum yields of up to 25 % at ambient temperature. The color of the emitted light significantly differs with the network structure. Furthermore, theoretical studies of singlet excitations in the molecular cluster, as well as NMR and mass-spectrometric investigations of the fragmentation of the metallopolymers in solution are described in detail.

[Hg4 Te8 (Te2 )4 ]8- : A Heavy Metal Porphyrinoid Embedded in a Lamellar Structure.

The use of ionic liquids (Cn C1 Im)[BF4 ] with long alkyl chains (n=10, 12) in the ionothermal treatment of Na2 [HgTe2 ] led to lamellar crystal structures with molecular macrocyclic anions [Hg8 Te16 ]8- (1), the heaviest known topological relative of porphyrin. [Hg8 Te16 ]8- differs from porphyrin by the absence of an electronic π-system, which prevents a "global" aromaticity. Quantum chemical studies reveal instead small ring currents in the pyrrole-type five-membered rings that indicate weak local (σ) aromaticity. As a result of their lamellar nature, the compounds are promising candidates for the formation of sheets containing chalcogenidometalate anions.

[Co@Sn6 Sb6 ]3- : An Off-Center Endohedral 12-Vertex Cluster.

We report on the asymmetric occupation of a 12-vertex cluster centered by a single metal atom. Three salts of related intermetalloid cluster anions, [Co@Sn6 Sb6 ]3- (1), [Co2 @Sn5 Sb7 ]3- (2), and [Ni2 @Sn7 Sb5 ]3- (3) were synthesized, which have pseudo-C4v -symmetric or pseudo-D4h -symmetric 12-vertex Sn/Sb shells and interstitial Co- ions or Ni atoms. Anion 1 is a very unusual single-metal-"centered" 12-atom cluster, with the inner atom being clearly offset from the cluster center for energetic reasons. Quantum chemistry served to assign atom types to the atomic positions and relative stabilities of this cluster type. The studies indicate that the structures are strictly controlled by the total valence electron count-which is particularly variable in ternary intermetalloid cluster anions. Preliminary 119 Sn NMR studies in solution, supported by quantum-chemical calculations of the shifts, illustrate the complexity regarding Sn:Sb distributions of such ternary systems.

Vibrational circular dichroism spectra for large molecules and molecules with heavy elements.

We present an implementation of vibrational circular dichroism (VCD) spectra in TURBOMOLE. We mainly followed the route proposed by Cheeseman [Chem. Phys. Lett. 252, 211 (1996)] and extended the modules for calculating the magnetic response and vibrational frequencies accordingly. The implementation allows for gauge origin invariant employment of effective core potentials, as demonstrated for Co(ppy)3, ppy = 2-Phenylpyridine. In this way, scalar relativistic effects are covered and heavy elements can be treated. Further, with the present implementation molecular symmetry may be efficiently exploited, which makes the calculation of large (symmetric) systems feasible. The calculation of the VCD spectrum of icosahedral C6202+ is shown as an illustrative application.

A Boron-Fluorinated Tris(pyrazolyl)borate Ligand ((F) Tp*) and Its Mono- and Dinuclear Copper Complexes [Cu((F) Tp*)2 ] and [Cu2 ((F) Tp*)2 ]: Synthesis, Structures, and DFT Calculations.

Reaction of [Si(3,5-Me2 pz)4 ] (1) with [Cu(MeCN)4 ][BF4 ] (2) gave the mono- and dinuclear copper complexes [Cu2 ((F) Tp*)2 ] (3) and [Cu((F) Tp*)2 ] (4). Both complexes contain the so-far unprecedented boron-fluorinated (F) Tp* ligand ([FB(3,5-Me2 pz)3 ](-) with pz=pyrazolyl) originating from 1, acting as a pyrazolyl transfer reagent, and the [BF4 ](-) counter anion of 2, serving as the source of the {BF} entity. The solid-state structures as well as the NMR and EPR spectroscopic characteristics of the complexes were elaborated. Pulsed gradient spin echo (PGSE) experiments revealed that 3 retains (almost entirely) its dimeric structure in benzene, whereas dimer cleavage and formation of acetonitrile adducts, presumably [Cu((F) Tp*)(MeCN)], is observed in acetonitrile. The short Cu⋅⋅⋅Cu distance of 269.16 pm in the solid-state is predicted by DFT calculations to be dictated by dispersion interactions between all atoms in the complex (the Cu-Cu dispersion contribution itself is only very small). As revealed by cyclic voltammetry studies, 3 shows an irreversible (almost quasi-reversible at higher scan rates) oxidation process centred at E(pa) =-0.23 V (E(0) 1/2 =-0.27 V) (vs. Fc/Fc(+) ). Oxidation reactions on a preparative scale with one equivalent of the ferrocenium salt [Fc][BF4 ] (very slow reaction) or air (fast reaction) furnished blue crystals of the mononuclear copper(II) complex [Cu((F) Tp*)2 ] (4). As expected for a Jahn-Teller-active system, the coordination sphere around copper(II) is strongly distorted towards a stretched octahedron, in accordance with EPR spectroscopic findings.

[(Pb6I8){Mn(CO)5}6](2-): an octahedral (M6X8)-like cluster with inverted bonding.

[BMIm]2[{PbMn(CO)5)}6I8] (BMIm: 1-butyl-3-methylimidazolium) is obtained by ionic liquid mediated reaction of PbI2 and Mn2(CO)10. Central is a cubelike (Pb6I8) unit containing a nonfilled Pb6 octahedron. Each Pb of this (Pb6I8) unit is terminated on its outside by Mn(CO)5, exhibiting Pb-Mn metal-to-metal bonding (280 pm). Structurally, the (Pb6I8) unit is similar to the well-known octahedral (M6Xn) cluster-type family (M = Zr, Nb, Ta, Mo, W; X = Cl, Br, I). In contrast to most similar cluster compounds, such as W6Br12 ([W6Br8]Br2/1Br4/2, according to Niggli notation) or the carbonyl cluster [Sn6{Cr(CO5)6}](2-), however, the nonfilled central Pb6 octahedron in [{PbMn(CO)5)}6I8](2-) does not exhibit any metal-to-metal bonding. Structure and bonding of the title compound are validated by single-crystal structure analysis, energy-dispersive X-ray analysis (EDX), infrared spectroscopy (FT-IR), and density functional theory (DFT) calculations. Based on the isolobal principle, electronegativity considerations, bond lengths, and DFT calculations including Mulliken population analysis and natural population analysis (NPA), in sum, the charge distribution of Pb is best reflected by an oxidation state of +1.

An Efficient Coupled-Perturbed Kohn-Sham Implementation of NMR Chemical Shift Computations with Local Hybrid Functionals and Gauge-Including Atomic Orbitals.

Nuclear shielding calculations for local hybrid (LH) functionals with position-dependent exact-exchange admixtures within a coupled-perturbed Kohn-Sham (CPKS) framework have been implemented into the Turbomole code using efficient seminumerical integration techniques to deal with two-electron integrals. When using gauge-including atomic orbitals, LHs generate additional terms within the "pre-loop" section of the CPKS scheme compared to global hybrid (GH) functionals, related to perturbed electron-repulsion integrals. These terms have been implemented and tested in detail, together with dependencies on grid sizes and integral screening procedures. Even with relatively small grids, a seminumerical treatment of GHs reproduces analytical GH results with high accuracy while improving scaling with system and basis-set sizes significantly. The extra terms generated by LHs in the pre-loop part increase the scaling of that contribution slightly, but the advantages compared to the analytical scheme are largely retained, in particular for the typically large basis sets used in NMR shift calculations, allowing for a very efficient computational scheme. An initial comparison of four first-generation LHs based on LDA exchange for a shielding test set of 15 small main-group molecules against high-level CCSD(T) benchmark data indicates a substantial reduction of the systematically underestimated shieldings compared to semilocal functionals or GHs for non-hydrogen nuclei when a so-called t-LMF is used to control the position dependence of the exact-exchange admixture. In contrast, proton shieldings are underestimated with this LMF, while an LH with a so-called s-LMF performs much better. These results are discussed in the context of experience for other properties, and they suggest directions for further improvements of LHs regarding nuclear shieldings.

Calculation of Magnetic Shielding Constants with meta-GGA Functionals Employing the Multipole-Accelerated Resolution of the Identity: Implementation and Assessment of Accuracy and Efficiency.

We present a highly efficient implementation for density functional calculations of chemical shielding constants. It employs the multipole-accelerated resolution of the identity for the calculation of the Coulomb part, which complements the usage of low order scaling routines for the evaluation of the exchange-correlation part and the Hartree-Fock exchange part. Introduced errors for shifts of chemical shielding constants of H, C, F, and P are evaluated for respective test sets of molecules and are related to the accuracy of shifts obtained with hybrid and nonhybrid functionals of the generalized gradient approximation type as well as for meta-GGA functionals themselves. Efficiency is demonstrated for α-d-glucose chains with more than 2500 atoms on a single CPU as well as with an OpenMP parallelized version.

Multicomponent reactions provide key molecules for secret communication.

A convenient and inherently more secure communication channel for encoding messages via specifically designed molecular keys is introduced by combining advanced encryption standard cryptography with molecular steganography. The necessary molecular keys require large structural diversity, thus suggesting the application of multicomponent reactions. Herein, the Ugi four-component reaction of perfluorinated acids is utilized to establish an exemplary database consisting of 130 commercially available components. Considering all permutations, this combinatorial approach can unambiguously provide 500,000 molecular keys in only one synthetic procedure per key. The molecular keys are transferred nondigitally and concealed by either adsorption onto paper, coffee, tea or sugar as well as by dissolution in a perfume or in blood. Re-isolation and purification from these disguises is simplified by the perfluorinated sidechains of the molecular keys. High resolution tandem mass spectrometry can unequivocally determine the molecular structure and thus the identity of the key for a subsequent decryption of an encoded message.

(Ge2P2)2-: a binary analogue of P4 as a precursor to the ternary cluster anion [Cd3(Ge3P)3]3.

The novel binary P4 analogue (Ge2P2)2- proved to be a suitable precursor for heteroatomic cluster synthesis. Over time in solution, it rearranges to form (Ge7P2)2-, as shown by NMR studies and X-ray diffraction. Reactions of (Ge2P2)2- with CdPh2 afford [K(crypt-222)]3[Cd3(Ge3P)3], containing an unprecedented ternary cluster anion with a triangular Cd3 moiety.

An NHC-phosphinidenyl as a synthon for new group 13/15 compounds.

The parent phosphinidene SIMesPH (1) (SIMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) was treated with benzyl potassium to form the metalated species SIMesPK (2), which was used as a synthon for the new group 13/15 cycles and cage compounds [SIMesPGatBu2]2 (3), [SIMesP(GatBu2)2Cl] (4) and [K(SIMesP)3AltBu] (5).