Intermolecular interactions in polymorphs of the cyclic trimeric perfluoro-<Emphasis Type="Italic">ortho</Emphasis>-phenylene mercury from geometric,energetic and AIM viewpoints: DFT study and Hirshfeld surface analysis

Macrocyclic polydentate Lewis acids are of ongoing interest owing to their ability for molecular recognition of anions; however, deep understanding of the nature of supramolecular bonding in their crystals is still lacking. To solve this problem, we have analysed four polymorphic modifications A–D of cyclic trimeric perfluoro-ortho-phenylene mercury (1) by quantum chemical calculations of intermolecular pair interactions energy. In all polymorphs, the main structural motif is stacked columns, which are further connected to a three-dimensional structure with either ladder-shape interactions between parallel macrocycles or T-shape interactions between nearly perpendicular macrocycles. Both arrangements contribute almost equally to the stabilization of the crystal structure. According to DFT computational study of isolated dimers that correspond to the most energetically favourable molecular pairs, and topological analysis of electron density distribution, the stabilization of these dimers is governed by Hg···C and C···C interactions. Significant contribution also comes from F···C and Hg···F interactions, while the role of mercurophilic interactions and F···F contacts seems negligible. Statistical analysis of crystal structures of host–guest complexes of the macrocycle 1 using Voronoi polyhedra and Hirshfeld surfaces showed the same types of intermolecular interactions to be responsible for stabilization of its polymorphs and co-crystals.     

One‐Pot ‘On‐solvent’ Multicomponent Protocol for the Synthesis of Medicinally Relevant 4H‐Pyrano[3,2‐c]quinoline Scaffold

‘One‐pot’ AcONa‐catalyzed transformation of salicylaldehydes, malononitrile and 4‐hydroxy‐1‐methylquinolin‐2(1H)‐one in the presence of a minimal quantity of EtOH results in fast (3 min) and efficient formation of unknown 2‐amino‐4‐(2‐hydroxyaryl)‐6‐methyl‐5‐oxo‐5,6‐dihydro‐4H‐pyrano[3,2‐c]quinoline‐3‐carbonitriles in 85–98% yields, which are potential pharmaceutical agents for treating disorders responsive to the induction of apoptosis, antiproliferation, or vascular disruption. This efficient ‘on‐solvent’ approach to the 4H‐pyrano[3,2‐c]quinoline scaffold represents a novel synthetic concept for multicomponent reaction (MCR) strategy and allows to combine the synthetic virtues of conventional MCR with ecological benefits and convenience of facile ‘on‐solvent’ procedure.     

Calcium Carbide: A Unique Reagent for Organic Synthesis and Nanotechnology

Acetylene, HC≡CH, is one of the primary building blocks in synthetic organic and industrial chemistry. Several highly valuable processes have been developed based on this simplest alkyne and the development of acetylene chemistry has had a paramount impact on chemical science over the last few decades. However, in spite of numerous useful possible reactions, the application of gaseous acetylene in everyday research practice is rather limited. Moreover, the practical implementation of high‐pressure acetylene chemistry can be very challenging, owing to the risk of explosion and the requirement for complex equipment; special safety precautions need to be taken to store and handle acetylene under high pressure, which limit its routine use in a standard laboratory setup. Amazingly, recent studies have revealed that calcium carbide, CaC₂, can be used as an easy‐to‐handle and efficient source of acetylene for in situ chemical transformations. Thus, calcium carbide is a stable and inexpensive acetylene precursor that is available on the ton scale and it can be handled with standard laboratory equipment. The application of calcium carbide in organic synthesis will bring a new dimension to the powerful acetylene chemistry.     

Electron-induced attachment of chlorinated benzenes to Si(1 0 0)2 × 1

Thermal (300 K) and electron-induced reactions of benzene (Bz), chlorobenzene (ClPh), 1,2-dichlorobenzene (1,2-diClPh) and 1,4-dichlorobenzene (1,4-diClPh) with Si(1 0 0)2 × 1 have been examined by scanning tunneling microscopy (STM). Thermal reactions of Bz yielded predominantly the quadruply-σ-bound tight bridge, TB, configuration on top of the Si dimer-rows, For ClPh and 1,2-diClPh, which resembled one another, thermal reaction led with 45-50% yield to the doubly-σ-bound butterfly, BF, configuration, also on top of the dimer-row, and with 20% yield to a novel ‘displaced’, D, configuration to one side of a dimer-row. The adsorbate 1,4-diClPh was alone in favouring a configuration in which neighbouring dimer-rows were ‘linked’ (L) by a bright-feature centrally located between the dimer-rows. By ab initio calculation, we interpret D as due to the rupture of one C-Cl bond per adsorbate molecule, and L to the rupture of two C-Cl’s. The breaking of this weak bond is followed in the former case by attachment of the aromatic ring to one dimer-row, and in the latter to attachment to two adjacent dimer-rows. Application of a −5 V voltage pulse to the STM tip substantially increased the percentage of row-linking structures, L, for 1,4-diClPh, but neither −5 V nor +4-6 V volt pulses resulted in L-type binding of Bz. The postulated L product of 1,4-diClPh, with an aromatic ring linking the two inner Si atoms of adjacent dimer-rows and the two Cl’s on the outer Si atoms of the dimer-rows, is shown to be in accord with ab initio simulation of the observed STM image.     

Separability in distant Jauch-type hybrid macrostates of a quantum and a classical system

It is assumed that for a quantum system (Q) plus a classical one (C) that are in a distant state the actually measurable Hermitian operators are of the formA _kK b _k Q _k (A is any Hermitian operator forQ, and the decomposition _k Q _k =1 of the identity is, after von Neumann, characteristic forC). This leads to Jauch-type macrostates (classes of microstates or statistical operators) forQ+C. On the other hand, it is shown that in theQ+Q case the essence of quantum correlations are the conditional states (or statistical operators) of subsystem I and the reduced state _II. Along these lines, the correlation entities (as a complete set of invariants) for the macrostates of theQ+C system are derived, and it is shown that one can make an isomorphic transition from the-convex set of the latter to that of the hybrid macrostates ( _k ,p _k ) Here _k is the conditional state ofQ under the condition thatQ _k occurs onC, andp _k is a classical discrete probability distribution onK, taking the place of _II as the macrostate ofC. This study indirectly throws new light on the nonseparability in theQ+Q case by contrasting it with a well-understood separability in theC+C andQ+C cases.     

Electronic structure and chain-length effects in diplatinum polyynediyl complexes trans,trans-[(X)(R3P)2Pt(C triple bond C)(n)Pt(PR3)2(X)]: a computational investigation

Structure and bonding in the title complexes are studied using model compounds trans,trans-[(C6H5)(H3P)2Pt(C triple bond C)(n)Pt(PH3)2(C6H5)] (PtCxPt; x = 2n = 4-26) at the B3LYP/LACVP* level of density functional theory. Conformations in which the platinum square planes are parallel are very slightly more stable than those in which they are perpendicular (DeltaE = 0.12 kcal mol(-1) for PtC8Pt). As the carbon-chain length increases, progressively longer C triple bond C triple bonds and shorter triple bond C-C triple bond single bonds are found. Whereas the triple bonds in HCxH become longer (and the single bonds shorter) as the interior of the chain is approached, the PtC triple bond C triple bonds in PtCxPt are longer than the neighboring triple bond. Also, the Pt-C bonds are shorter at longer chain lengths, but not the H-C bonds. Accordingly, natural bond orbital charge distributions show that the platinum atoms become more positively charged, and the carbon chain more negatively charged, as the chain is lengthened. Furthermore, the negative charge is localized at the two terminal C triple bond C atoms, elongating this triple bond. Charge decomposition analyses show no significant d-pi* backbonding. The HOMOs of PtCxPt can be viewed as antibonding combinations of the highest occupied pi orbital of the sp-carbon chain and filled in-plane platinum d orbitals. The platinum character is roughly proportional to the Pt/Cx/Pt composition (e.g., x = 4, 31 %; x = 20, 6 %). The HOMO and LUMO energies monotonically decrease with chain length, the latter somewhat more rapidly so that the HOMO-LUMO gap also decreases. In contrast, the HOMO energies of HCxH increase with chain length; the origin of this dichotomy is analyzed. The electronic spectra of PtC4Pt to PtC10Pt are simulated. These consist of two pi-pi* bands that redshift with increasing chain length and are closely paralleled by real systems. A finite HOMO-LUMO gap is predicted for PtCinfinityPt. The structures of PtCxPt are not strictly linear (average bond angles 179.7 degrees -178.8 degrees ), and the carbon chains give low-frequency fundamental vibrations (x = 4, 146 cm(-1); x = 26, 4 cm(-1)). When the bond angles in PtC12Pt are constrained to 174 degrees in a bow conformation, similar to a crystal structure, the energy increase is only 2 kcal mol(-1). The above conclusions should extrapolate to (C triple bond C)(n) systems with other metal endgroups.     

Chemistry of functionalized benzazepines. 5. Synthesis and chemical transformation of the 1,2,4,5-tetrahydrospiro-[3H-2-benzazepine-3,1′-cycloalkanes]

The synthesis of new spiro derivatives of tetrahydro-2-benzazepine was accomplished and their nitration, bromination, allylation, acetylation, formylation and oxidation reactions were studied. Nitration and bromi-nation of 5-methyl(1,5-dimethyl)-1,2,4,5-tetrahydrospiro[3H-2-benzazepine-3,1-cycloalkane] took place regioselectively on position C-8 of the phenyl ring. A nitrone was obtained for the first time in the title series. The structures of the compounds were established by ir and nmr spcctroscopy.