Demeter Tzeli - Academia.edu (original) (raw)

Papers by Demeter Tzeli

Molecules/Molecules online/Molecules annual, May 23, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Molybdenum–Sulfur Bond: Electronic Structure of Low-Lying States of MoS

Journal of Physical Chemistry A, Feb 11, 2022

The molybdenum-sulfur bond plays an important role in many processes such as nitrogen-fixation, a... more The molybdenum-sulfur bond plays an important role in many processes such as nitrogen-fixation, and it is found as a building block in layered materials such as MoS2, known for its various shapes and morphologies. Here, we present an accurate theoretical and experimental investigation of the chemical bonding and the electronic structure of 20 low-lying states of the MoS molecule. Multireference and coupled cluster methodologies, namely, MRCISD, MRCISD + Q, RCCSD(T), and RCCSD[T], were employed in conjunction with basis sets up to aug-cc-pwCV5Z-PP/aug-cc-pwCV5Z for the study of these states. We note the significance of including the inner 4s24p6 electrons of Mo and 2s22p6 of S in the correlated space to obtain accurate results. Experimentally, the predissociation threshold of MoS was measured using resonant two-photon ionization spectroscopy, allowing for a precise measurement of the bond dissociation energy. Our extrapolated computational D0 value for the ground state is 3.936 eV, in excellent agreement with our experimental measurement of 3.932 ± 0.004 eV. The largest calculated adiabatic D0 (5.74 eV) and the largest dipole moment (6.50 D) were found for the 5Σ+ state, where a triple bond is formed. Finally, the connection of the chemical bonding of the isolated MoS species to the relevant solid, MoS2, is emphasized. The low-lying septet states of the diatomic molecule are involved in the material as a building block, explaining the stability and the variety of the shapes and morphologies of the material.

Journal of Physical Chemistry A, Jul 20, 2020

Multiple bonds between atoms are one of the most fundamental aspects of chemistry. Double and tri... more Multiple bonds between atoms are one of the most fundamental aspects of chemistry. Double and triple bonds are quite common, while quadruple bonds are a true oddity and very rare for the main group elements. Identifying molecules containing quadruple bonds is very important and, even more so, determining the necessary requirements for the existence of such bonds. Here we present high-level theoretical calculations on the isoelectronic MX molecules, i.e., TcN, RuC, RhB, and PdBe, showing that such a quadruple bond with main group elements is not that uncommon. We found that quadruple bonds are formed in their ground states X 3 Δ (TcN) and Χ 1 Σ + (RuC, RhB, and PdBe) and in the two lowest excited states of TcN (1 Σ + , 1 Δ), RuC (1,3 Δ), and RhB (1,3 Δ). The quadruple bonds consist of two π and two σ bonds: (4d xz −2p x) 2 , (4d yz −2p y) 2 , (4d z 2 −2p z) 2 , and 5s 0 ← 2s 2 (1 Σ +) or 5p z 0 ←2s 2 (1,3 Δ). Bond lengths, dissociation energies, dipole moments, spectroscopic parameters, and relative energy ordering of the states were calculated via multireference and coupled cluster methodology using the aug-cc-pV5Z X (-PP) M basis sets. We study how the atomic states involved and how the gradual transition from covalent to dative bond, from TcN to PdBe, influence all of the calculated data, such as bond dissociation energies, bond lengths, and relative energy ordering of the states. Finally, we report the requirements for the occurrence of such bonds in molecular systems. All Be, B, C, and N atoms combining with the appropriate second-row transition metal can form quadruple bonds, while they cannot form such bonds with the first-row transition metals.

An Efficient Light‐Mediated Protocol for the Direct Amide Bond Formation via a Novel Carboxylic Acid Photoactivation Mode by Pyridine‐CBr₄

Chemistry: A European Journal, May 3, 2023

The direct amide bond formation between a carboxylic acid and an amine still constitutes a challe... more The direct amide bond formation between a carboxylic acid and an amine still constitutes a challenging reaction for both academia and industry. We demonstrate herein that several pairs of amines (halogen bond acceptors) and organohalogen sources may be used for the photochemical amidation reaction under either UVA or sunlight irradiation. Our studies led to the identification of pyridine‐CBr4 as an efficient agent to perform amide synthesis under LED 370 nm irradiation, avoiding super‐stoichiometric quantities. An extended substrate scope was demonstrated, showing that the widely used amino and carboxyl protecting groups are compatible with this photochemical protocol, while a number of industrially interesting products and bioactive compounds were synthesized. Direct infusion‐high resolution mass spectrometry studies suggest an unprecedented type of carboxylic acid activation mode upon irradiation, involving the generation of a symmetric anhydride, an active ester with pyridine N‐oxide and a mixed anhydride with hypobromous acid.

DAE SOLID STATE PHYSICS SYMPOSIUM 2015, 2016

A series of 3-aryl-2-phenyl-3-phenylaminopropanoic acids is synthesized, isolated, and spectrosco... more A series of 3-aryl-2-phenyl-3-phenylaminopropanoic acids is synthesized, isolated, and spectroscopically and structurally elucidated. The effect of the substituents on the spectroscopic characteristics and conformations has been studied using IR, UV, and 1 H NMR spectroscopy. Theoretical quantum chemical calculations are performed with a view to explaining and supporting the experimental optical properties and electronic structure of the compounds studied.

Molecules, Apr 20, 2022

Ι. Δομές και ενέργειες αλληλεπιδράσεως των συστημάτων van der Waals C2H2-(H2O)x x=1 - 4 και CHy-H2O y=1 2 και ΙΙ. Ηλεκτρονιακή δομή των καρβιδίων BC BC- HBC AIC AIC- και HAIC μέσω ab initio υπολογισμών

Journal of Computational Chemistry, Apr 14, 2021

Quadruple bonding is uncommon for main group elements and the identification of species forming s... more Quadruple bonding is uncommon for main group elements and the identification of species forming such bonds is remarkably interesting particularly in diatomic anions for which there is a lack of information. Here, it is found that the MX − anions, TcN − , RuC − , RhB − , and PdBe − , present quadruple bonding, as do the corresponding MX

Chemical Physics Letters, Aug 1, 2010

In an ab initio calculation, when the inclusion of core electron correlation is required, the bes... more In an ab initio calculation, when the inclusion of core electron correlation is required, the best approach is to use a basis set developed for the electrons that are correlated. However, when a basis set is used that has not been developed for the number of the electrons which are correlated in a calculation, the quantities calculated (geometry, binding energies, frequencies, etc.) need to be corrected for the basis set superposition error. Several cases are discussed and the proper line of action is emphasized.

3-Input AND Molecular Logic Gate with Enhanced Fluorescence Output: The Key Atom for the Accurate Prediction of the Spectra

Journal of Chemical Information and Modeling, Apr 19, 2022

The development of artificial receptors for sensing and recognition of species, as well as for ad... more The development of artificial receptors for sensing and recognition of species, as well as for advanced logic functions, is a significant challenge in the field of molecular information technology. Here, we study theoretically, via DFT/TD-DFT calculations, the photophysical properties of a 3-input AND molecular logic gate which presents an enhanced fluorescence spectrum. It was found that the geometry conformation at an N atom of the piperazine group is the key factor for the correct calculation of the absorption spectra of the calculated structures. Its geometry is between tetrahedral and planar, while changes in the corresponding CNCC dihedral angle of about 10 degrees can cause significant shifts of the main peak of the absorption spectra up to 100 nm. Moreover, the unusually enhanced fluorescence of a molecular logic gate (MLG) is explained. Finally, we conclude that molecular systems having N atoms, whose geometry is between planar and tetrahedral, can be ideal molecules as sensors and molecular logic gates. Our calculated absorption and emission spectra are in excellent agreement with available experimental data.

The electron affinity of gallium nitride (GaN) and digallium nitride (GaNGa): The importance of the basis set superposition error in strongly bound systems

Journal of Chemical Physics, Apr 8, 2008

Breaking covalent bonds in the context of the many-body expansion (MBE). I. The purported “first row anomaly” in XH_n (X = C, Si, Ge, Sn; n = 1–4)

Journal of Chemical Physics, Jun 28, 2022

We present a new, novel implementation of the Many-Body Expansion (MBE) to account for the breaki... more We present a new, novel implementation of the Many-Body Expansion (MBE) to account for the breaking of covalent bonds, thus extending the range of applications from its previous popular usage in the breaking of hydrogen bonds in clusters to molecules. A central concept of the new implementation is the in situ atomic electronic state of an atom in a molecule that casts the one-body term as the energy required to promote it to that state from its ground state. The rest of the terms correspond to the individual diatomic, triatomic, etc., fragments. Its application to the atomization energies of the XHn series, X = C, Si, Ge, Sn and n = 1–4, suggests that the (negative, stabilizing) 2-B is by far the largest term in the MBE with the higher order terms oscillating between positive and negative values and decreasing dramatically in size with increasing rank of the expansion. The analysis offers an alternative explanation for the purported “first row anomaly” in the incremental Hn−1X–H bond energies seen when these energies are evaluated with respect to the lowest energy among the states of the XHn molecules. Due to the “flipping” of the ground/first excited state between CH2 (3B1 ground state, 1A1 first excited state) and XH2, X = Si, Ge, Sn (1A1 ground state, 3B1 first excited state), the overall picture does not exhibit a “first row anomaly” when the incremental bond energies are evaluated with respect to the molecular states having the same in situ atomic states.

On the dipole moment of the ground state X 3Δ of iron carbide, FeC

Journal of Chemical Physics, Mar 15, 2003

Theoretical investigation of the ground and low-lying excited states of gallium and indium silicides, GaSi and InSi

Journal of Chemical Physics, Dec 21, 2009

Journal of Chemical Physics, Aug 28, 2022

We examine the Many-Body Expansion (MBE) for alkaline earth metal clusters, Ben, Mgn, Can (n = 4,... more We examine the Many-Body Expansion (MBE) for alkaline earth metal clusters, Ben, Mgn, Can (n = 4, 5, 6) at the MP2, CCSD(T), MRPT2, and MRCI levels of theory. The magnitude of each term in the MBE is evaluated for several geometrical configurations. We find that the behavior of the MBE for these clusters depends strongly on the geometrical arrangement, and, to a lesser extent, on the level of theory used. Another factor that affects the MBE is the in situ (ground or excited) electronic state of the individual atoms in the cluster. For most geometries, the three-body term is the largest, followed by a steady decrease in absolute energy for subsequent terms. Though these systems exhibit non-negligible multi-reference effects, there was little qualitative difference in the MBE expansion when employing single vs. multi-reference methods. Useful insights into the connectivity and stability of these clusters have been drawn from the respective potential energy surfaces and Quasi-Atomic orbitals for the various dimers, trimers, and tetramers. Through these analyses we investigate the similarities and differences in the binding energies of different size clusters for these metals.

Journal of Physical Chemistry A, Sep 28, 2005

We have studied 40 states of the diatomic iron carbide cation FeC + by multireference methods cou... more We have studied 40 states of the diatomic iron carbide cation FeC + by multireference methods coupled with relatively large basis sets. For most of the states, we have constructed complete potential energy curves, reporting dissociation energies, usual spectroscopic parameters, and bonding mechanisms for the lowest of the studied states. The ground state is of 2 ∆ symmetry, with the first excited state (a 4 Σ-) lying 18 kcal/mol higher. The X 2 ∆ state displays a triple-bond character, with an estimated D 0 value of 104 kcal/mol with respect to the adiabatic products or 87 kcal/mol with respect to the ground-state fragments.

Theoretical investigation of the ground and low-lying excited states of nickel carbide, NiC

Journal of Chemical Physics, May 21, 2007

Journal of Physical Chemistry A, Jul 20, 2001

Continuing our study on the electronic structure of the carbides BC and AlC (Tzeli, D.; Mavridis,... more Continuing our study on the electronic structure of the carbides BC and AlC (Tzeli, D.; Mavridis, A. J. Phys. Chem. A 2001, 105, 1175), we have investigated the electronic structure of 29 and 30 excited states of the BC and AlC molecules, respectively, by ab initio quantum mechanical multireference methods and quantitative basis sets. For both diatomic species we report complete potential energy curves, total energies, interatomic distances, dissociation energies, dipole moments, Mulliken charges, energy gaps, and usual spectroscopic constants. Our results are, in general, in good to very good agreement with the existing experimental values.

Electronic structure and bonding of the 3d transition metal borides, MB, M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu through all electron ab initio calculations

Journal of Chemical Physics, Jan 17, 2008

Journal of the American Chemical Society, Mar 3, 2020

Supramolecular capsules are desirable containers for the study of molecular behavior in small spa... more Supramolecular capsules are desirable containers for the study of molecular behavior in small spaces and offer applications in transport, catalysis, and material science. We report here the use of chalcogen bonding to form container assemblies that are stable in water. Cavitands 1−3 functionalized with 2,1,3-benzoselenadiazole walls were synthesized in good yield from resorcin[4]arenes. The solid-state single-crystal X-ray structure of 3 showed a dimeric assembly cemented together through multiple Se•••N chalcogen bonds. Binding of hydrophobic and amphiphilic guests in D 2 O was investigated by 1 H NMR methods and revealed host−guest assemblies of 1:1, 2:1, and 2:2 stoichiometries. Small guests such as n-hexane or cyclohexane assembled as 2:2 capsular complexes, larger guests like cyclohexane carboxylic acid or cyclodecane formed 1:1 cavitand complexes, and longer linear guests like ndodecane, cyclohexane carboxylic acid anhydride, and amides created 2:1 capsular complexes. The 2:1 complex of the capsule with cyclohexane carboxylic acid anhydride was stable over 2 weeks, showing that the seam of chalcogen bonds is "waterproof". Selective uptake of cyclohexane over benzene and methyl cyclohexane over toluene was observed in aqueous solution with the capsule. Hydrophobic forces and hydrogen-bonding attractions between guest molecules such as 3-methylbutanoic acid stabilized the assemblies in the presence of the competing effects of water. The high polarizability and modest electronegativity of Se provide a capsule lining complementary to guest C−H bonds. The 2,1,3benzoselenadiazole walls impart an unusually high magnetic anisotropy to the capsule environment, which is supported by density functional theory calculations.