On the inter-ring torsion potential of regioregular P3HT: a first principles reexamination with explicit side chains

Poly(3-alkylthiophene) is a family of conjugated semicrystalline polymers for organic electronic applications. Crucial for the fine-tuning of such systems is a detailed understanding of the correlation between molecular structure/morphology and electronic properties. However, a series of a priori assumptions is commonly made in order to deduce macromolecular-scale geometric and energetic features from those of rather small homologous molecular systems. Alkyl side chains are routinely shortened (if not systematically removed) during such high-accuracy ab initio calculations in order to reduce their conformational space. We will show through first principles calculations on a monosubstituted bithiophene molecule how a full-length alkyl fragment can influence both side chain energetics and backbone flexibility in alkylthiophene-based polymers and copolymers. Folded side chains, characterized by a gauche arrangement of the second torsion angle from the ring, are found to be substantially favoured over extended ones, thanks to a network of CH–π hydrogen-bond-like interactions with both aromatic rings. Trans-planar (conjugated) arrangements of limit-ordered crystalline models, and cisoid sequences suitable for the investigation of chain-folding phenomena, are also discussed in detail

Chain statistics in polyethylene crystallization

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Kinetic trapping of 2,4,6-tris(4-pyridyl)benzene and ZnI2 into M12L8 poly-[n]-catenanes using solution and solid-state processes

: Here, we show that in a supramolecular system with more than 20 building blocks forming large icosahedral M12L8 metal-organic cages (MOCs), using the instant synthesis method, it is possible to kinetically trap and control the formation of interlocking M12L8 nanocages, giving rare M12L8 TPB-ZnI2 poly-[n]-catenane. The catenanes are obtained in a one-pot reaction, selectively as amorphous (a1) or crystalline states, as demonstrated by powder X-ray diffraction (powder XRD), thermogravimetric (TG) analysis and 1H NMR. The 300 K M12L8 poly-[n]-catenane single crystal X-ray diffraction (SC-XRD) structure including nitrobenzene (1) indicates strong guest binding with the large M12L8 cage (i.e., internal volume ca. 2600 Å3), allowing its structural resolution. Conversely, slow self-assembly (5 days) leads to a mixture of the M12L8 poly-[n]-catenane and a new TPB-ZnI2 (2) coordination polymer (i.e., thermodynamic product), as revealed by SC-XRD. The neat grinding solid-state synthesis also yields amorphous M12L8 poly-[n]-catenane (a1'), but not coordination polymers, selectively in 15 min. The dynamic behavior of the M12L8 poly-[n]-catenanes demonstrated by the amorphous-to-crystalline transformation upon the uptake of ortho-, meta- and para-xylenes shows the potential of M12L8 poly-[n]-catenanes as functional materials in molecular separation. Finally, combining SC-XRD of 1 and DFT calculations specific for the solid-state, the role of the guests in the stability of the 1D chains of M12L8 nanocages is reported. Energy interactions such as interaction energies (E), lattice energies (E*), host-guest energies (Ehost-guest) and guest-guest energies (Eguest-guest) were analysed considering the X-ray structure with and without the nitrobenzene guest. Not only the synthetic control achieved in the synthesis of the M12L8 MOCs but also their dynamic behavior either in the crystalline or amorphous phase are sufficient to raise scientific interest in areas ranging from fundamental to applied sides of chemistry and material sciences

Exploring short intramolecular interactions in alkylaromatic substrates

From proteins and peptides to semiconducting polymers, aliphatic chains on aromatic groups are recurring motifs in macromolecules from very diverse application fields. Fields in which molecular folding and packing determine the macroscopic physical properties that make such advanced materials appealing in the first place. Within each macromolecule, the intrinsic structure of each unit defines how it interacts with its neighbours, ultimately opening up or denying certain backbone conformations. This eventually also determines how macromolecules interact with each other. This account deals specifically with the conformational problem of many common alkylaromatic units, examining the features of an intramolecular interaction involving a side chain with as few as three methylene groups. A set of 23 model compounds featuring an intramolecular interaction between an aliphatic X-H (X = C, N, O, and S) bond and an aromatic ring was considered. Quantitative computational analysis was made possible, thanks to complete basis set extrapolated CCSD(T) calculations and NCI topological analysis, the latter of which revealed an elaborate network of dispersive and steric interactions leading to somewhat unintuitive and unexpected results, such as the higher energetic stability of certain twisted conformational isomers over those with extended side chains. Vicinal covalent effects from polarizing groups and various heteroatoms, along with the occurrence of non-dispersive phenomena, were also investigated. The conclusions drawn from the investigation include a comprehensive set of guidelines intended to aid in the prediction of the most stable conformation for this class of building blocks. Our findings affect a variety of different research fields, including the tailoring of functional materials for organic electronics and photovoltaics, with insights into a rational treatment of conformational disorder, and the study of protein- and peptide-folding preferences, putting an emphasis on peculiar interactions between the backbone and aromatic residues

A Combined Experimental and Theoretical Study on the Stereodynamics of Monoaza[5]helicenes: Solvent-Induced Increase of the Enantiomerization Barrier in 1-Aza-[5]helicene

Helicenes and heterohelicenes are attractive compounds with great potential in materials sciences to be used in optoelectronics as ligand backbones in enantioselective catalysis and as chiral sensors.[1] Synthetic protocols were developed to obtain helicenes with skeletons consisting of ortho-fused benzene rings or analogue structures incorporating a heteroatom, as in thiophene-, furane-, or pyridine-containing helicenes.[2] In recent years, a repertoire of synthetic strategies was developed to access all monoaza[5]helicenes as well as some diaza[ 5]helicenes.[3] The properties of these materials are related to the stereodynamics of these helical chiral compounds. By exploration of the unexpected broad range of physicochemical properties of aza[n]helicenes it was realized that there is an opportunity to modulate a specific property by controlled design of the position of the N atoms in the helical molecular frame. In this contribution, we show a complete stereodynamic characterization of monoaza[5]-helicenes combining enantioselective dynamic HPLC and DFT calculations. At variance with previous theoretical calculations[4], 1-aza[5]helicene shows a surprisingly high enantiomerization barrier, which is triggered by specific solvent interactions. [5] References [1] a) H. A. Staab, M. A. Zirnstein, C. Krieger, Angew. Chem. Int. Ed. Engl. 1989, 28, 86–88; Angew. Chem. 1989, 101, 73– 75;b) T. R. Kelly, Acc. Chem. Res. 2001, 34, 514 –522; c) T. J. Wigglesworth, D. Sud, T. B. Norsten, V. S. Lekhi, N. R. Branda, J. Am. Chem. Soc. 2005, 127, 7272 – 7273; d) L. Vyklicky´, S. H. Eichhorn, T. J. Katz, Chem. Mater. 2003, 15, 3594 –3601; e) M. Gingras, Chem. Soc. Rev. 2013, 42, 1051– 1095. [2] a) M. Gingras, Chem. Soc. Rev. 2013, 42, 968–1006; b) M. Gingras, G. F_lix, R. Peresutti, Chem. Soc. Rev. 2013, 42, 1007 –1050; c) Y. Shen, C.-F. Chen, Chem. Rev. 2012, 112, 1463– 1535. [3] a) C. Bazzini, S. Brovelli, T. Caronna, C. Gambarotti, M. Giannone, P. Macchi, F. Meinardi, A. Mele, W. Panzeri, F. Recupero, A. Sironi, Eur. J. Org. Chem. 2005, 1247 – 1257; b) S. Abbate, C. Bazzini, T. Caronna, F. Fontana, C. Gambarotti, F. Gangemi, G. Longhi, A. Mele, I. Natali Sora, W. Panzeri, Tetrahedron 2006, 62,139 –148; c) T. Caronna, F. Fontana, A. Mele, I. Natali Sora, W. Panzeri, L. Vigan_, Synthesis 2008, 413– 416; d) T. Caronna, S. Gabbiadini, A. Mele, F. Recupero, Helv. Chim. Acta 2002, 85, 1 –8; e) T. Caronna, F. Castiglione, F. Fontana, D. Mendola, I. Natali Sora, Molecules 2012, 17, 463 –479. [4] S. Abbate, C. Bazzini, T. Caronna, F. Fontana, F. Gangemi, F. Lebon, G. Longhi, A. Mele, I. Natali Sora, Inorg. Chim. Acta 2007, 360, 908 –912. [5] T. Caronna, A. Mele, A. Famulari, D. Mendola, F. Fontana, M. Juza, M. Kamuf, K. Zawatzky, and O. Trapp, Chem. Eur. J. 2015, 21, 1–7

Can a whole nanoparticle accurately describe a single C60 fullerene when it comes to weak electrostatic interactions?

technologically-relevant processes, from printing and powder coating to the removal of fine dust from coal-fired power plant emissions. C60 fullerene, owing to its peculiar mechanical and electronic properties, has been oftentimes used as a model nanoparticle in the study of e.g. cluster conductivity and Coulomb fission, allowing for a deeper understanding on e.g. cluster polarizability and charge transfer among spherical or nearly-spherical particles. Several classical models describing the interaction between two spherical particles or a spherical particle and a point charge can be found in literature, involving either metallic or dielectric particles [1]. However, attaching macroscopic properties, such as dielectric or metallic character, to a nanometer-sized object is not straightforward. The C60 case has in fact spawned what is now an on-going debate on the matter [2-6]. In this talk, new insights from DFT simulation of neutral C60 molecules interacting with selected electron donors and acceptors are presented, and compared to both literature model interactions (in which point charges are preferred to chemically meaningful ligands) and classical model interactions. [1] E.B. Lindgren et al. Phys. Chem. Chem. Phys. 18 (2016) 5883. [2] A.J. Stace et al. Phys. Chem. Chem. Phys. 13 (2011) 18339. [3] H. Zettergren et al. Phys. Chem. Chem. Phys. 14 (2012) 16360. [4] G. Raggi et al. Phys. Chem. Chem. Phys. 15 (2013) 20115. [5] H. Zettergren et al. Phys. Chem. Chem. Phys. 16 (2014) 14969. [6] F. Lindén et al. J. Chem. Phys. 145 (2016) 194307

Insights into the formation of chiral second sphere coordination complexes with aromatic tris amines: combined single crystal X-ray crystallography and molecular modeling analyses

Control over the formation of non-centrosymmetric chiral materials is highly desirable due to their potential applications in areas such as ferroelectricity, piezo- and pyroelectricity, and second harmonic generation.[1] Unfortunately, the development of a reliable approach to induce the formation of a chiral material from achiral molecules remains a great challenge in the field of molecular chemistry.[2] Furthermore, the understanding of the driving forces behind those aggregations is a prerequisite for the design and construction of chiral molecular arrays. C3-symmetrical tripodal molecules have emerged as attractive organic frameworks for the construction of chiral coordination compounds.[3] In the present contribution we report about a family of isostructural, chiral supramolecular networks obtained in the solid state by exploiting second sphere coordination interactions in the self-assembly of achiral tris amines L1 and L2 with tetrahalometallate and halide ions. Quantum-Mechanical calculations (including the usage of approaches specific for crystalline solid phases) provided important insights into the intramolecular and packing interactions which determine chirality, pointing to a direct effect of the methyl groups of the central benzene ring of the tris amines. [4] References [1] (a) P. A. Maggard, C. L. Stern and K. R. Poeppelmeier, J. Am. Chem. Soc., 2001, 123, 7742–7743; (b) M. Liu, L. Zhang and T. Wang, Chem. Rev., 2015, DOI: 10.1021/ Q5 cr500671p. [2] P. S. Halasyamani and K. R. Poeppelmeyer, Chem. Mater., 1998, 10, 2753–2769. [3] Z. Dai and J. W. Canary, New J. Chem., 2007, 31, 1708–1718. [4] H. Yu, L. Li, J. Gao, J. Tong, W. Zheng, M. Cametti, A. Famulari, S.V. Meille, F. Guo and J. Martí-Rujas Journal Article Dalton Trans., 2015,44, 15960-15965. DOI: 10.1039/C5DT02387D, Pape

東北地方における気候の長期変動

平成11年度共同利用研究集会「北日本の気象と海象」（1999年8月18日～19日, 研究代表者：児玉安正）の講演要旨Atmospheric and oceanographic phenomena around the northern part of Japan(Abstracts of scientific symposia held at Otsuchi Marine Research Center in 1999

Mechanochemical dehydrochlorination and chelation reaction in the solid state: from a molecular salt to a coordination complex

We report the solid state structural transformation of a hydrogen bonded complex salt into a metal complex via dehydrochlorination using mechanochemistry. A crystalline salt containing a large and flexible bidentate dication hydrogen bonded to a tetrachlorometalate (II) anion has been ground in the presence of KOH. Substitution of charge-assisted hydrogen bonding interactions by coordination bonds via chelation has been demonstrated by single-crystal and powder X-ray diffraction analysis. By-product water molecules are included in the structure, playing an important role establishing electrostatic interactions. The irreversibility property of the transformation of the coordination complex into a hydrogen bonded complex salt was determined experimentally. Density functional calculations were used to attempt a rationalisation of the structural results into the mechanochemical reactions

EPR characterization of the heme domain of a self-sufficient cytochrome P450 (CYP116B5)

CYP116B5 is a self-sufficient cytochrome P450 (CYP450) with interesting catalytic properties for synthetic purposes. When isolated, its heme domain can act as a peroxygenase on different substrates of biotechnological interest. Here, by means of continuous wave and advanced EPR techniques, the coordination environment of iron in the isolated CYP116B5 heme domain (CYP116b5hd) is characterized. The ligand-free protein shows the characteristic EPR spectrum of a low-spin (S = 1/2) FeIII-heme with gz = 2.440 ± 0.005, gy = 2.25 ± 0.01, gx = 1.92 ± 0.01]. These g-values reflect an electronic ground state very similar to classical P450 monooxygenases rather than P450 peroxygenases. Binding of imidazole results in g-values very close to the ones reported for CYP152 peroxygenases. The detection of hyperfine interactions through HYperfine Sub-level CORrElation (HYSCORE) Spectroscopy experiments, shows that this is due to a nitrogen-mediated axial coordination. This work adds a piece of experimental evidence to the research, aimed at elucidating the features that distinguish the classical P450 enzymes from peroxygenases. It shows that the electronic environment of heme iron of CYP116B5 in the resting state is similar to the classical P450 monooxygenases. Therefore, it is not the critical factor that confers to CYP116B5hd its peroxygenase-like activity, suggesting a crucial role of the protein matrix. © 2022 The Author