scholarly journals Photoluminescent Coordination Polymers Based on Group 12 Metals and 1H-Indazole-6-Carboxylic Acid

Inorganics ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 20
Author(s):  
Antonio A. García-Valdivia ◽  
Estitxu Echenique-Errandonea ◽  
Gloria B. Ramírez-Rodríguez ◽  
José M. Delgado-López ◽  
Belén Fernández ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Coordination Polymers ◽  
Density Functional ◽  
Free Ligand ◽  
Emission Spectra ◽  
Point Of View ◽  
Theoretical Point ◽  
Fourier Transformed Infrared Spectroscopy ◽  
3D Network ◽  
The Stability

Two new coordination polymers (CPs) based on Zn(II) and Cd(II) and 1H-indazole-6-carboxylic acid (H2L) of general formulae [Zn(L)(H2O)]n (1) and [Cd2(HL)4]n (2) have been synthesized and fully characterized by elemental analyses, Fourier transformed infrared spectroscopy and single crystal X-ray diffraction. The results indicate that compound 1 possesses double chains in its structure whereas 2 exhibits a 3D network. The intermolecular interactions, including hydrogen bonds, C–H···π and π···π stacking interactions, stabilize both crystal structures. Photoluminescence (PL) properties have shown that compounds 1 and 2 present similar emission spectra compared to the free-ligand. The emission spectra are also studied from the theoretical point of view by means of time-dependent density-functional theory (TD-DFT) calculations to confirm that ligand-centred π-π* electronic transitions govern emission of compound 1 and 2. Finally, the PL properties are also studied in aqueous solution to explore the stability and emission capacity of the compounds.

Synthesis, Structure, and Visible Phosphorescence Emission of Novel CuI Coordination Polymers Based on 4,4′-Bis(3-pyridyl)-2,2′-bis(hydroxylmethyl) Biphenyl

2015 ◽  
Vol 68 (2) ◽  
pp. 307 ◽  
Author(s):  
Guo-Xia Jin ◽  
Jian-Ping Ma ◽  
Chuan-Zhi Sun ◽  
Yu-Bin Dong
Keyword(s):  
Coordination Polymers ◽  
Density Functional ◽  
Room Temperature ◽  
Emission Spectra ◽  
Density Functional Theory Calculations ◽  
X Ray Diffraction ◽  
Ligand Charge Transfer ◽  
Yellow Orange ◽  
The Difference ◽  
1D Chains

Four new CuI coordination polymers, [(CuCl)L]n (1), {[(CuCl)2L2]·(H2O)}n (2), [(CuBr)L]n (3), and {[(CuBr)2L2]·(H2O)}n (4), were obtained from a new ligand 4,4′-bis(3-pyridyl)-2,2′-bis(hydroxylmethyl) biphenyl (L) and characterized by single-crystal X-ray diffraction. In 1 and 3, the rhombic [Cu2(μ-X)2] units are connected to each other by the bidentate linkers to form an infinite 1D double chain (X = Cl, Br). Such 1D chains are arranged into a 2D sheet through inter-chain π···π interactions. In 2 and 4, there are similar 1D double chains, but different inter-chain arrangement. Such 1D chains are connected into a 2D layer and further arranged in an ABAB fashion through O–H···X hydrogen bonds. The emission spectra and lifetimes in the microsecond range were measured at room temperature and at 77 K. Complexes 1 and 3 exhibit strong orange and yellow–orange emission in the solid state at room temperature, and were assigned to X-and M-to-ligand charge transfer excited states based on density functional theory calculations. The emission property of 2 and 4 was distinctly different from that of 1 and 3, probably due to the difference in coordination environments of the CuI centres as well as the dissimilar intermolecular arrangement.

scholarly journals Cu-Doped KCl Unfolded Band Structure and Optical Properties Studied by DFT Calculations

2020 ◽  
Author(s):  
Cesar Castillo-Quevedo ◽  
Jose Luis Cabellos ◽  
Raul Aceves ◽  
Roberto Núñez-González ◽  
Alvaro Posada-Amarillas
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Copper Ions ◽  
Point Of View ◽  
Basis Set ◽  
Theoretical Point ◽  
Conduction Bands ◽  
Cu Substitution ◽  
Effect Of Copper

The unfolded band structure and optical properties of Cu-doped KCl crystals were computed by first principles within the framework of density functional theory, implemented in the ABINIT electronic structure package utilizing pseudopotential approximation and a plane-wave basis set. From a theoretical point of view, Cu substitution into pristine KCl crystals requires calculation by the supercell (SC) method. This procedure shrinks the Brillouin zone, resulting in a folded band structure that is difficult to interpret. To solve this problem and gain insight into the effect of copper ions (Cu+) on electronic properties, the band structure of SC KCl:Cu was unfolded to make a direct comparison with the band structure of the primitive cell (PC) of pristine KCl. To understand the effect of Cu substitution on optical absorption, we calculated the imaginary part of the dielectric function of KCl:Cu through a sum-over-states formalism and broke it down into different band contributions by partially making an iterated cumulative sum (ICS) of selected valence and conduction bands. Consequently, we identified those interband transitions that give rise to the absorption peaks due to the Cu+ ion. These transitions involve valence and conduction bands formed by the Cu-3d and Cu-4s electronic states

The Absorption of Diamondoids from Time-dependent Density Functional Calculations

2011 ◽  
Vol 1370 ◽  
Author(s):  
Márton Vörös ◽  
Tamás Demjén ◽  
Adam Gali
Keyword(s):  
Density Functional ◽  
Quantum Confinement Effect ◽  
Infrared Region ◽  
Point Of View ◽  
Time Dependent ◽  
Theoretical Point ◽  
Hybrid Functional ◽  
Energy Part ◽  
Td Dft ◽  
Bulk Diamond

ABSTRACTDiamondoids are small diamond nanocrystals with perfect hydrogenated surfaces. Recent absorption measurements showed that the spectrum of diamondoids exhibit features that are not understood from the theoretical point of view, e.g. optical gaps are only slightly larger than the gap of bulk diamond which runs against the quantum confinement effect. Previous calcula-tions, even beyond standard density functional theory (DFT), failed to obtain the experimental optical gaps (Eg) of diamondoids. We show that all-electron time-dependent DFT (TD-DFT) calculations including the PBE0 hybrid functional in the TD-DFT kernel are able to provide quantitatively accurate results. Our calculations demonstrate that Rydberg transitions govern the low energy part of the absorption spectrum, even for relatively large nanodiamonds result-ing in low Eg. Since the optical gap of these diamondoids lies in the ultraviolet spectral re-gion, we investigated whether simple adsorbates of the surface are able to shift the gap towards the infrared region. We found that a double bonded sulfur atom at the surface results in a sub-stantial gap reduction.

scholarly journals Stability and Optical Absorption of a Comprehensive Virtual Library of Minimal Eumelanin Oligomer Models

2021 ◽  
Author(s):  
jun wang ◽  
Lluís Blancafort
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Level Structure ◽  
Point Of View ◽  
Chemical Diversity ◽  
Quinone Methide ◽  
Minimal Models ◽  
Functional Theory ◽  
Living Organisms ◽  
The Stability

Eumelanin is the black biopolymer responsible for photoprotection in living organisms. Lack of knowledge of the atomic-level structure limits understanding of its function and exploitation of its potential in material science. To overcome these limitations, we present a systematic density functional theory study of the stability and optical properties of a library of 830 dimers of 5,6-dihydroxyindole (DHI), which are minimal models of eumelanin oligomers. Our aim is to understand the principles that govern the formation of DHI oligomers, relate the optical properties of the dimers with their stability, and establish their possible role in the photophysics of the biopolymer. From the structural point of view, we find a preference for oxidized over reduced and cyclic over linear structures, which speaks in favor of polycyclic graphite-like structures for the larger oligomers. We present an electrocyclization mechanism leading to the cyclic structures. We also find that besides the widely considered quinone and quinone methide oxidation patterns where two heteroatoms per DHI fragment are oxidized, dimers with one or three oxidized sites per fragment and an interfragment double bond are also stable and may be present in eumelanin. As far as the optical properties are concerned, some oxidized dimers combine relative stability with absorption energies as low as 1.3 eV. Such fragments may be present as substructures in the naturally found oligomers and might have a relevant contribution to the absorption spectrum of the biopolymer. In addition to these insights into the struc-tural and optical properties of the oligomers, we introduce a new classification scheme and a representative set of 53 dimers combining thermodynamic stability with chemical diversity.<br>

Theoretical Study on the Antioxidant Activity of Alizarin, Purpurin, and Pseudopurpurin

2011 ◽  
pp. 130-140 ◽  
Author(s):  
Ruifa Jin ◽  
Hongzheng Bao ◽  
Yin Bai ◽  
Xiuhua Li
Keyword(s):  
Density Functional Theory ◽  
Antioxidant Activity ◽  
Density Functional ◽  
Polyphenolic Compounds ◽  
Point Of View ◽  
Cytotoxic Activities ◽  
Theoretical Point ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
High Antioxidant Activity

Hydroxyanthraquinone derivatives are a large group of natural polyphenolic compounds found widely in plants. The cytotoxic activities of hydroxyanthraquinone derivatives have been demonstrated using cancer cell lines. The pharmacological effect can be explained by their antioxidant activity and their inhibition of certain enzymes. There are two main kinds of mechanism, H-atom transfer and one-electron transfer, by which antioxidants can play their role. The structural and electronic properties of hydroxyanthraquinone derivatives, alizarin, purpurin, pseudopurpurin, and their radicals were investigated using density functional theory. It turned out that these three molecules appear to be good candidates for high antioxidant activity species, particularly for pseudopurpurin. Taking this system as an example, we present an efficient method for the investigation of antioxidant activity for such kind of hydroxyanthraquinone derivatives from theoretical point of view. With the current work, we hope to highlight the antioxidant activity of hydroxyanthraquinone derivatives and stimulate the interest for further studies and exploitation in pharmaceutical industry.

scholarly journals Experimental Conditions for the Stabilization of the Lyotropic Biaxial Nematic Mesophase

Crystals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 158
Author(s):  
Erol Akpinar ◽  
Antônio Figueiredo Neto
Keyword(s):  
Nematic Phase ◽  
Liquid Crystalline ◽  
Point Of View ◽  
Theoretical Point ◽  
Experimental Conditions ◽  
The Third ◽  
Nematic Phases ◽  
The Stability ◽  
Biaxial Nematic ◽  
Biaxial Nematic Phase

Nematic phases are some of the most common phases among the lyotropic liquid crystalline structures. They have been widely investigated during last decades. In early studies, two uniaxial nematic phases (discotic, ND, and calamitic, NC) were identified. After the discovery of the third one, named biaxial nematic phase (NB) in 1980, however, some controversies in the stability of biaxial nematic phases began and still continue in the literature. From the theoretical point of view, the existence of a biaxial nematic phase is well established. This review aims to bring information about the historical development of those phases considering the early studies and then summarize the recent studies on how to stabilize different nematic phases from the experimental conditions, especially, choosing the suitable constituents of lyotropic mixtures.

scholarly journals From Oligo(Phenyleneethynylene) Monomers to Supramolecular Helices: The Role of Intermolecular Interactions in Aggregation

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3530
Author(s):  
Berta Fernández ◽  
Zulema Fernández ◽  
Emilio Quiñoá ◽  
Félix Freire
Keyword(s):  
Density Functional Theory ◽  
Self Assembly ◽  
Density Functional ◽  
Point Of View ◽  
Basis Set ◽  
Theoretical Point ◽  
Functional Theory ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Supramolecular helices that arise from the self-assembly of small organic molecules via non-covalent interactions play an important role in the structure and properties of the corresponding materials. Here we study the supramolecular helical aggregation of oligo(phenyleneethynylene) monomers from a theoretical point of view, always guiding the studies with experimentally available data. In this way, by systematically increasing the number of monomer units, optimized n-mer geometries are obtained along with the corresponding absorption and circular dichroism spectra. For the geometry optimizations we use density functional theory together with the B3LYP-D3 functional and the 6–31G** basis set. For obtaining the spectra we resort to time-dependent density functional theory using the CAM-B3LYP functional and the 3–21G basis set. These combinations of density functional and basis set were selected after systematic convergence studies. The theoretical results are analyzed and compared to the experimentally available spectra, observing a good agreement.

ELECTRONIC STRUCTURE AND PHOTOCHEMISTRY OF INORGANIC PHOTOCHROMIC COMPLEX [Cu(N,N′-DIETHYLETHYLENEDIAMINE)2]2+: PLANAR–TETRAHEDRAL GEOMETRY CHANGE ACCOMPANIED WITH d9–d10 ELECTRONIC TRANSITION

2006 ◽  
Vol 05 (04) ◽  
pp. 887-894 ◽  
Author(s):  
HIROTOSHI MORI ◽  
KAZUMI ISHII ◽  
EISAKU MIYOSHI
Keyword(s):  
Electronic Structure ◽  
Reaction Mechanism ◽  
Density Functional ◽  
Point Of View ◽  
Isomerization Reaction ◽  
Theoretical Point ◽  
Orbital Theory ◽  
Tetrahedral Geometry ◽  
In Trans ◽  
Cis Isomer

A photo-induced geometry isomerization reaction mechanism of a photochromic inorganic complex, [ Cu ( dieten )2]2+ (dieten = N,N ′-diethyletylenediamine), was investigated with density functional molecular orbital theory calculations. A new stable cis-isomer that is assigned to a photo-irradiated (PI) phase was found. In the PI geometry, two N,N ′-diethyl groups are placed more closely than in the most stable low-temperature (LT) phase, and the complex has a slightly twisted structure with steric hindrance. Recently, Takahashi et al. have suggested that two ethyl groups were in trans position in the PI phase from the EXAFS and XANES observation; however, no energy minimum corresponds to such a PI state was found. The photochromic reaction mechanism and electronic structure of [ CuII ( dieten )2]2+ are discussed from a theoretical point of view.

scholarly journals How Does One Understand the Stability of Political Regimes from a Theoretical Point of View?

Politeja ◽  
2019 ◽  
Vol 16 (6(63)) ◽  
pp. 111-123
Author(s):  
Łukasz Perlikowski
Keyword(s):  
Subject Matter ◽  
Political Change ◽  
Point Of View ◽  
Theoretical Point ◽  
Political Regimes ◽  
Main Subject ◽  
Political Concept ◽  
Political Theories ◽  
The Stability

The investigations of this paper revolve around the concept of stability. We would like to make several analytical distinctions which would allow us to differentiate between various concepts of stability. The background of our work is the theory of political change supported by examples of this kind presented by Plato, Polybius, James Harrington, Jean-Jacques Rousseau, and Aristotle.The paper includes some remarks on Hobbes’s and Hume’s theories of stability which, strictly speaking, can be smoothly subsumed under a modern political concept thereof. Also worthy of note is the specification of the main subject-matter of political theories in terms of the problem of stability. Finally, we propose a sketch of the map of the problem of stability

scholarly journals Cu-Doped KCl Unfolded Band Structure and Optical Properties Studied by DFT Calculations

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4300
Author(s):  
César Castillo-Quevedo ◽  
Jose Luis Cabellos ◽  
Raul Aceves ◽  
Roberto Núñez-González ◽  
Alvaro Posada-Amarillas
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Copper Ions ◽  
Point Of View ◽  
Basis Set ◽  
Theoretical Point ◽  
Conduction Bands ◽  
Cu Substitution ◽  
Effect Of Copper

The unfolded band structure and optical properties of Cu-doped KCl crystals were computed by first principles within the framework of density functional theory, implemented in the ABINIT software program, utilizing pseudopotential approximation and a plane-wave basis set. From a theoretical point of view, Cu substitution into pristine KCl crystals requires calculation by the supercell (SC) method. This procedure shrinks the Brillouin zone, resulting in a folded band structure that is difficult to interpret. To solve this problem and gain insight into the effect of copper ions (Cu+) on electronic properties, the band structure of SC KCl:Cu was unfolded to make a direct comparison with the band structure of the primitive cell (PC) of pristine KCl. To understand the effect of Cu substitution on optical absorption, we calculated the imaginary part of the dielectric function of KCl:Cu through a sum-over-states formalism and broke it down into different band contributions by partially making an iterated cumulative sum (ICS) of selected valence and conduction bands. Consequently, we identified those interband transitions that give rise to the absorption peaks due to the Cu+ ion. These transitions involve valence and conduction bands formed by the Cu-3d and Cu-4s electronic states.

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