Vibrational Analysis of Benziodoxoles and Benziodazolotetrazoles

Tetrazoles are well known for their high positive enthalpy of formation which makes them attractive as propellants, explosives, and energetic materials. As a step towards a deeper understanding of the stability of benziodazolotetrazole (BIAT)-based materials compared to their benziodoxole (BIO) counterparts, we investigated in this work electronic structure features and bonding properties of two monovalent iodine precursors: 2-iodobenzoic acid and 5-(2-iodophenyl)tetrazole and eight hypervalent iodine (III) compounds: I-hydroxybenzidoxolone, I-methoxybenziodoxolone, I-ethoxybenziodoxolone, I-iso-propoxybenziodoxolone and the corresponding I-hydroxyben ziodazolotetrazole, I-methoxybenziodazolotetrazole, I-ethoxybenziodazolotetrazole and I-iso- propoxybenziodazolotetrazole. As an efficient tool for the interpretation of the experimental IR spectra and for the quantitative assessment of the I−C, I−N, and I−O bond strengths in these compounds reflecting substituent effects, we used the local vibrational mode analysis, originally introduced by Konkoli and Cremer, complemented by electron density and natural bond orbital analyses. Based on the hypothesis that stronger bonds correlate with increased stability, we predict that, for both series, i.e., substituted benziodoxoles and benziodazolotetrazoles, the stability increases as follows: I-iso-propoxy < I-ethoxy < I-methoxy < I-hydroxy. In particular, the I−N bonds in the benziodazolotetrazoles could be identified as the so-called trigger bonds being responsible for the initiation of explosive decomposition in benziodazolotetrazoles. The new insight gained by this work will allow for the design of new benziodazolotetrazole materials with controlled performance or stability based on the modulation of the iodine bonds with its three ligands. The local mode analysis can serve as an effective tool to monitor the bond strengths, in particular to identify potential trigger bonds. We hope that this article will foster future collaboration between the experimental and computational community being engaged in vibrational spectroscopy.

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Metal–Halogen Bonding Seen through the Eyes of Vibrational Spectroscopy

Materials ◽

10.3390/ma13010055 ◽

2019 ◽

Vol 13 (1) ◽

pp. 55 ◽

Cited By ~ 5

Author(s):

Vytor P. Oliveira ◽

Bruna L. Marcial ◽

Francisco B. C. Machado ◽

Elfi Kraka

Keyword(s):

Density Functional ◽

Halogen Bonding ◽

Fine Tuning ◽

Mode Analysis ◽

Planar Geometry ◽

Local Mode ◽

Special Role ◽

Bonded Materials ◽

Local Vibrational Mode ◽

Donor And Acceptor

Incorporation of a metal center into halogen-bonded materials can efficiently fine-tune the strength of the halogen bonds and introduce new electronic functionalities. The metal atom can adopt two possible roles: serving as halogen acceptor or polarizing the halogen donor and acceptor groups. We investigated both scenarios for 23 metal–halogen dimers trans-M(Y2)(NC5H4X-3)2 with M = Pd(II), Pt(II); Y = F, Cl, Br; X = Cl, Br, I; and NC5H4X-3 = 3-halopyridine. As a new tool for the quantitative assessment of metal–halogen bonding, we introduced our local vibrational mode analysis, complemented by energy and electron density analyses and electrostatic potential studies at the density functional theory (DFT) and coupled-cluster single, double, and perturbative triple excitations (CCSD(T)) levels of theory. We could for the first time quantify the various attractive contacts and their contribution to the dimer stability and clarify the special role of halogen bonding in these systems. The largest contribution to the stability of the dimers is either due to halogen bonding or nonspecific interactions. Hydrogen bonding plays only a secondary role. The metal can only act as halogen acceptor when the monomer adopts a (quasi-)planar geometry. The best strategy to accomplish this is to substitute the halo-pyridine ring with a halo-diazole ring, which considerably strengthens halogen bonding. Our findings based on the local mode analysis provide a solid platform for fine-tuning of existing and for design of new metal–halogen-bonded materials.

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Local Vibrational Mode Analysis of π–Hole Interactions between Aryl Donors and Small Molecule Acceptors

Crystals ◽

10.3390/cryst10070556 ◽

2020 ◽

Vol 10 (7) ◽

pp. 556 ◽

Cited By ~ 2

Author(s):

Seth Yannacone ◽

Marek Freindorf ◽

Yunwen Tao ◽

Wenli Zou ◽

Elfi Kraka

Keyword(s):

Vibrational Mode ◽

Interaction Strength ◽

Substituent Effects ◽

Lone Pair ◽

Water Dimer ◽

Mode Analysis ◽

New Members ◽

Local Vibrational Mode ◽

Hole Interaction ◽

Secondary Bonding

11 aryl–lone pair and three aryl–anion π –hole interactions are investigated, along with the argon–benzene dimer and water dimer as reference compounds, utilizing the local vibrational mode theory, originally introduced by Konkoli and Cremer, to quantify the strength of the π –hole interaction in terms of a new local vibrational mode stretching force constant between the two engaged monomers, which can be conveniently used to compare different π –hole systems. Several factors have emerged which influence strength of the π –hole interactions, including aryl substituent effects, the chemical nature of atoms composing the aryl rings/ π –hole acceptors, and secondary bonding interactions between donors/acceptors. Substituent effects indirectly affect the π –hole interaction strength, where electronegative aryl-substituents moderately increase π –hole interaction strength. N-aryl members significantly increase π –hole interaction strength, and anion acceptors bind more strongly with the π –hole compared to charge neutral acceptors (lone–pair donors). Secondary bonding interactions between the acceptor and the atoms in the aryl ring can increase π –hole interaction strength, while hydrogen bonding between the π –hole acceptor/donor can significantly increase or decrease strength of the π –hole interaction depending on the directionality of hydrogen bond donation. Work is in progress expanding this research on aryl π –hole interactions to a large number of systems, including halides, CO, and OCH3− as acceptors, in order to derive a general design protocol for new members of this interesting class of compounds.

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A Critical Evaluation of Vibrational Stark Effect (VSE) Probes with the Local Vibrational Mode Theory

Sensors ◽

10.3390/s20082358 ◽

2020 ◽

Vol 20 (8) ◽

pp. 2358 ◽

Cited By ~ 4

Author(s):

Niraj Verma ◽

Yunwen Tao ◽

Wenli Zou ◽

Xia Chen ◽

Xin Chen ◽

...

Keyword(s):

Electric Field ◽

Stark Effect ◽

Comprehensive Evaluation ◽

Critical Evaluation ◽

Normal Modes ◽

Mode Analysis ◽

Local Mode ◽

Underlying Assumption ◽

Local Vibrational Mode ◽

Internal Coordinates

Over the past two decades, the vibrational Stark effect has become an important tool to measure and analyze the in situ electric field strength in various chemical environments with infrared spectroscopy. The underlying assumption of this effect is that the normal stretching mode of a target bond such as CO or CN of a reporter molecule (termed vibrational Stark effect probe) is localized and free from mass-coupling from other internal coordinates, so that its frequency shift directly reflects the influence of the vicinal electric field. However, the validity of this essential assumption has never been assessed. Given the fact that normal modes are generally delocalized because of mass-coupling, this analysis was overdue. Therefore, we carried out a comprehensive evaluation of 68 vibrational Stark effect probes and candidates to quantify the degree to which their target normal vibration of probe bond stretching is decoupled from local vibrations driven by other internal coordinates. The unique tool we used is the local mode analysis originally introduced by Konkoli and Cremer, in particular the decomposition of normal modes into local mode contributions. Based on our results, we recommend 31 polyatomic molecules with localized target bonds as ideal vibrational Stark effect probe candidates.

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Substituent effects in benzene derivatives—a local mode analysis of ring CH stretching overtone spectra of methylated and chlorinated benzenes

Spectrochimica Acta Part A Molecular Spectroscopy ◽

10.1016/0584-8539(84)80029-x ◽

1984 ◽

Vol 40 (1) ◽

pp. 57-61 ◽

Cited By ~ 11

Author(s):

Ryoichi Nakagaki ◽

Ichiro Hanazaki

Keyword(s):

Substituent Effects ◽

Mode Analysis ◽

Local Mode ◽

Benzene Derivatives ◽

Chlorinated Benzenes ◽

Local Mode Analysis

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Towards Computational Screening for New Energetic Molecules: Calculation of Heat of Formation and Determination of Bond Strengths by Local Mode Analysis

Frontiers in Chemistry ◽

10.3389/fchem.2021.726357 ◽

2021 ◽

Vol 9 ◽

Author(s):

Imogen L. Christopher ◽

Adam A. L. Michalchuk ◽

Colin R. Pulham ◽

Carole A. Morrison

Keyword(s):

Solid State ◽

Gas Phase ◽

Energetic Materials ◽

Inorganic Compounds ◽

Heats Of Formation ◽

Mode Analysis ◽

Local Mode ◽

Reliable Determination ◽

Computational Screening

The reliable determination of gas-phase and solid-state heats of formation are important considerations in energetic materials research. Herein, the ability of PM7 to calculate the gas-phase heats of formation for CNHO-only and inorganic compounds has been critically evaluated, and for the former, comparisons drawn with isodesmic equations and atom equivalence methods. Routes to obtain solid-state heats of formation for a range of single-component molecular solids, salts, and co-crystals were also evaluated. Finally, local vibrational mode analysis has been used to calculate bond length/force constant curves for seven different chemical bonds occurring in CHNO-containing molecules, which allow for rapid identification of the weakest bond, opening up great potential to rationalise decomposition pathways. Both metrics are important tools in rationalising the design of new energetic materials through computational screening processes.

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Paradox of Small Particles in the Pulsed Laser Initiation of Explosive Decomposition of Energetic Materials

Физика горения и взрыва ◽

10.15372/fgv20160214 ◽

2016 ◽

Keyword(s):

Energetic Materials ◽

Pulsed Laser ◽

Explosive Decomposition ◽

Laser Initiation ◽

Small Particles

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Electrostatic effects on ionization equilibria: An MNDO study of proton and hydrogen transfer reactions of 4-fluorobutylamine

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19900001 ◽

1990 ◽

Vol 55 (1) ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Zdeněk Friedl ◽

Stanislav Böhm

Keyword(s):

Hydrogen Transfer ◽

Substituent Effects ◽

Radical Cations ◽

Transfer Reactions ◽

Protonated Forms ◽

Minor Part ◽

Bond Strengths ◽

Ionization Equilibria ◽

A Minor ◽

Gas Phase Basicities

The relative enthalpies of proton transfer δ ΔH0and homolytic bond strengths δDH0(B-H+) were calculated by the MNDO method for the sp and ap conformers of 4-flurobutylamine. The data obtained, along with the experimental gas phase basicities, are compared with the values predicted by the electrostatic theory. It is shown that the substituent polar effects FD on the basicities of amines are predominantly due to interactions in their protonated forms (X-B-H+) and/or radical-cations (X-B+.), those in the neutral species (X-B) playing a minor part. A contribution, which is considerably more significant in the sp conformer than in the ap conformer, arises probably also from substituent effects on the homolytic bond strength DH0(B-H+.

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