: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Adsorption isotherm models: Classification, physical meaning, application and solving method

Supramolecular catalysis is a rapidly expanding discipline which has benefited from the development of both homogeneous catalysis and supramolecular chemistry. The properties of classical metal and organic catalysts can now be carefully tailored by means of several suitable approaches and the choice of reversible interactions such as hydrogen bond, metal–ligand, electrostatic and hydrophobic interactions. The first part of these two subsequent reviews will be dedicated to catalytic systems for which non-covalent interactions between the partners of the reaction have been designed although mimicking enzyme properties has not been intended. Ligand, metal, organocatalyst, substrate, additive, and metal counterion are reaction partners that can be held together by non-covalent interactions. The resulting catalysts possess unique properties compared to analogues lacking the assembling properties. Depending on the nature of the reaction partners involved in the interactions, distinct applications have been accomplished, mainly (i) the building of bidentate ligand libraries (intra ligand–ligand), (ii) the building of di- or oligonuclear complexes (inter ligand–ligand), (iii) the alteration of the coordination spheres of a metal catalyst (ligand–ligand additive), and (iv) the control of the substrate reactivity (catalyst–substrate). More complex systems that involve the cooperative action of three reaction partners have also been disclosed. In this review, special attention will be given to supramolecular catalysts for which the observed catalytic activity and/or selectivity have been imputed to non-covalent interaction between the reaction partners. Additional features of these catalysts are the easy modulation of the catalytic performance by modifying one of their building blocks and the development of new catalytic pathways/reactions not achievable with classical covalent catalysts.

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Supramolecular catalysis. Part 1: non-covalent interactions as a tool for building and modifying homogeneous catalysts.

Cyanobacterial extracellular polymeric substances (EPS) are mainly composed of high-molecular-mass heteropolysaccharides, with variable composition and roles according to the microorganism and the environmental conditions. The number of constituents - both saccharidic and nonsaccharidic - and the complexity of structures give rise to speculations on how intricate their biosynthetic pathways could be, and how many genes may be involved in their production. However, little is known regarding the cyanobacterial EPS biosynthetic pathways and regulating factors. This review organizes available information on cyanobacterial EPS, including their composition, function and factors affecting their synthesis, and from the in silico analysis of available cyanobacterial genome sequences, proposes a putative mechanism for their biosynthesis.

Complexity of cyanobacterial exopolysaccharides: composition, structures, inducing factors and putative genes involved in their biosynthesis and assembly

An sp-hybridized all-carboatomic ring, cyclo[18]carbon: Electronic structure, electronic spectrum, and optical nonlinearity

Intermolecular interaction characteristics of the all-carboatomic ring, cyclo[18]carbon: Focusing on molecular adsorption and stacking

An sp-hybridized all-carboatomic ring, cyclo[18]carbon: Bonding character, electron delocalization, and aromaticity

Recently, Iyakutti and coworkers published an interesting paper studying characteristics of cyclo[12]carbon and cyclo[18]carbon as well as their interactions with graphene (Mater. Sci. and Eng. B 263 (2021) 114895). However, we found some of their calculations are obviously unreasonable and a few conclusions are misleading. Here, we make some remarks on this paper according to common theoretical chemistry knowledge and our recent research experiences on cyclo[n]carbon systems, and meantime we revisit the interaction between the cyclo[18]carbon and graphene using a more reliable calculation model in combination with some novel analysis methods to provide complementary viewpoint to Iyakutti's work.

Zeyu Liu

Papers

An sp-hybridized all-carboatomic ring, cyclo[18]carbon: Electronic structure, electronic spectrum, and optical nonlinearity

Intermolecular interaction characteristics of the all-carboatomic ring, cyclo[18]carbon: Focusing on molecular adsorption and stacking

An sp-hybridized all-carboatomic ring, cyclo[18]carbon: Bonding character, electron delocalization, and aromaticity

Comment on “18 and 12 – Member carbon rings (cyclo[n]carbons) – A density functional study”

Potential optical molecular switch: Lithium@cyclo[18]carbon complex transforming between two stable configurations