Substitution Of Halogen Atoms Research Articles

Inorganic/organic sublattice roles in band edge photodynamics of isoelectronically substituted hybrid semiconductors

Zero-dimensional organic–inorganic hybrid metal halides are unique semiconductors with fruitful physical properties. Usually, only the inorganic polyhedrons dominate the band edge electronic and photophysical properties of such hybrid semiconductors, whereas the organic components mainly act as structure-stabilizing units. Herein, we study the electronic structures and photodynamics of isoelectronically Br-substituted (I) zero-dimensional organic–inorganic copper halide semiconductors (C9H14N)3Cu3(BrxI1−x)6. They are composed of both inorganic [Cu3(BrxI1−x)6]3− units and organic C9H14N+ skeletons. It is surprising to find that unlike usual organic–inorganic metal halides, although the heavily isoelectronic substitution of halogen atoms in the (C9H14N)3Cu3I6 crystal leads to significant shrinkage of the lattice, it does not remarkably alter the bandgap and luminescence peak owing to the site-projected density of states as revealed by the density functional theory calculation. The inorganic units dominate the valence band edge quantum states, whereas the organic skeletons dominate the conduction-band edge states. However, the isoelectronic substitution significantly lowers the symmetry of the crystal, and as a result, the quantum transition probability at the band edge increases first and decreases then with increasing concentration of substituting bromine atoms. The (C9H14N)3Cu3(BrxI1−x)6 crystals exhibit dual-band luminescence with large Stokes shift and near-unity quantum yield. It arises from the excitons trapped by two kinds of centers. The critical participation of the organic skeletons in the electronic structures and band edge photodynamics refresh our knowledge of their roles in the hybrid semiconductors.

Terminal group engineering of oligothiophene donors for efficient organic solar cells

All-small-molecule organic solar cells exhibit high reproducibility than polymer-based cells. Benzodithiophene and oligothiophene based derivatives are the most widely studied small molecule donors. The lower synthetic complexity and superior stability make oligothiophene based derivatives more promising for large scale production. Recently, a thiazole-centered oligothiophene donor Tz6T yields a high efficiency but deserves further improving. Substitution of halogen atoms on the end groups is proven to affect molecular packing through various non-covalent intermolecular interactions. Here we adopt terminal group engineering to regulate the optoelectronic properties of Tz6T. Through chlorine substitution, highest efficiency (9.60 %) is achieved in Tz6T-PH-Cl-4: eC9-4F binary device. Our results shed light on the structure-function relationship, and provide valuable insights into the regulation of phase separation.

Effects of halogen atom substitution on luminescent radicals: a case study on tris(2,4,6-trichlorophenyl)methyl radical-carbazole dyads.

A series of halogen-substitute carbazole TTM radicals was synthesized. The effect of halogen substituents on radical luminescence was systematically evaluated. It was found that the well-known heavy atom effect does not work in the emission of radicals and that halogen substitution of the donor carbazole can change the HOMO and alter the absorption and emission wavelengths. In addition, the photostability was found to be improved with respect to TTM but not significantly different from that of closed-shell fluorescent molecules.

Exploring the potential of inorganic cubic halide perovskites RbSrM3 (M=Cl, Br) for advanced optoelectronic applications: A DFT study

Halide perovskites, being a large family attained researchers focus for multiple targets because of their outstanding properties and flexible chemistry. In this study, density functional theory (DFT) based on WIEN2K code were utilized, to thoroughly explore the structural, electronic, optical, and mechanical properties of inorganic cubic halide perovskites, i.e.; RbSrM3 (M = Cl, Br) for optoelectronic applications. Variation in the lattice parameters and unit cell volume were observed, as a result of halogen atom substitution from Cl with Br. Subsequently, the electronic characteristics certify the direct bandgap nature, with bandgap values of 7.73 eV for RbSrCl3 and 6.79 eV for RbSrBr3, respectively. Optical properties proposed the high optical absorption, high conductivity, and low reflectivity. Further analysis into the mechanical properties, including bulk modulus (B), shear modulus (G), young modulus (E), anisotropic factor (A), Poison’s ratio (ν), and Pugh’s ratio (B/G), comply the near ductility, stiffness, and elastically anisotropic behavior, confirmed the stability and reliability of the designed compound. Debye temperature (θD), showing high capability to withstand against heat produced by lattice vibrations, further associated the thermodynamic stability that support the formation energy calculations. Based on the findings, it is confidently suggested that investigated halide perovskite materials i.e.; RbSrM3 (M = Cl, Br), are promising candidates for next-generation photodetectors and optoelectronic devices.

Study on the modulating effect of halogen atom substitution on the detection range of water content detection probes in organic solvents

Fluorescence probes based on the variations of aggregation state (Aggregation-Induced Emission (AIE) and Aggregation-Caused Quenching (ACQ)) have received widespread attention due to their simplicity, efficiency and intuitiveness. However, typical probes are highly sensitive to changes in polarity and slight variations in the external environment can cause a complete change in the aggregation state. With the aim of expanding the detection range of the molecular probe, this work adopts a different design strategy from adjusting the molecular backbone but regulates the fluorescence behavior of the Schiff base molecular backbone by introducing different halogen atoms. Systematic studies show that when chlorine serves as substitutional atoms (3,5-Cl Salen), the probe can achieve full-range detection of water content (0–100 vol%) in ethanol and DMF. To our knowledge, the 3,5-Cl Salen represents the best water content probe in organic molecules. Experimental and theoretical studies have shown that the adjustment of halogen atoms can linearly change the charge distribution on the benzene ring and precisely control the strength of intermolecular interactions. At the same time, we developed a fluorescent filter paper based on 3,5-Cl Salen and used smartphones for rapid, sensitive and precise on-site measurement of water content in organic solvents.

P … π Bonds in Complexes of C2H2 … PH2X (X = H, F, Cl, Br, I): Quantum Chemical Analysis

Non-covalent bonds take a strong in numerous chemical and biological phenomena, bringing them to the forefront of research. We studied the structure and interaction properties of C2H2 and PH2X using quantum chemistry following the Moller-Plesset method (MP2). The results showed that C2H2 and PH2X could form a stable complex (C2H2 … PH2X (X= H, F, Cl, Br, I)) of Cs symmetry. The halogen X was far away from the C2H2 molecule, and the P atom was not directly above the center of the C≡C bond. The molecular interaction energy of C2H2 … PH2X varied between -6.3 and -14.5 kJ/mol. This revealed the generation of a long-range weak interaction. Analysis of the interaction energy revealed that the substitution of halogen atoms promoted the formation of the complex (C2H2 … PH2X). The interaction energy of the complex decreased in the order F>Cl>Br>I, which was consistent with the change in electronegativity of the halogen atoms. Independent Gradient Model (IGM) analysis calculations showed that van der Waals interaction was the dominant weak interaction in C2H2 … PH2X. The symmetry-adapted perturbation theory (SAPT) was used to study the system, and the results revealed that the interactions in C2H2 … PH3, C2H2 … PH2I were primarily dispersive, and the interactions in C2H2 … PH2F, C2H2 … PH2Cl, C2H2 … PH2Br were primarily electrostatic.

Role of organic cations in tuning the exciton binding energy of 2D lead iodide perovskite derivatives

Control over the exciton binding energy (Eb) in two-dimensional (2D) perovskites can enable their application in a broad range of optoelectronic technologies. To investigate the effects of organic cations on the excitonic properties of 2D perovskites, films of lead iodide hybrids basing on four structurally similar cations of phenylethylammonium (PEA), 4-florophenylethylammonium (FPEA), 4-chlorophenylethylammonium (ClPEA) and 4-bromophenylethylammonium (BrPEA) were prepared and their optical properties were characterized. Results show that both the perovskite layer distortion and exciton absorption/emission peak do not vary too much by the substitution of halogen atom in the para H of phenylethyl cation. Further examination of the temperature-dependent exciton emission properties reveals that the thermal activation energy Ea, which can also be regarded as exciton binding energy in our work, can be tuned over ca. 170 meV within the set of hybrids. It is found that exciton binding energy is sensitive to the identity of organic cations and to the resulting PbI6 octahedron distortion. Among the compounds considered, FPEA based perovskite has the biggest PbI6 octahedron distortion and the largest calculated Ea of 330 meV, while the Br-PEA based perovskite shows a smaller octahedron distortion and the lowest calculated Ea. We believe that an enhanced polarizability of organic cations may be responsible for the observed decrease in octahedra distortion and Ea for the p-halophenylethylammonium lead iodide perovskite derivatives.

How Halogenation Impacts the Polymer Backbone Conformation: Learning from Combination of Solid‐State MAS NMR and X‐Ray Scattering

AbstractOver the past decade, halogenated semiconducting polymers have attracted considerable interest due to their outstanding optoelectronic properties. Thus, in most of today's organic photovoltaic devices benchmark organic semiconductors are halogenated materials, either electron donor polymers or non‐fullerene acceptor (NFA) small molecules. However, the nature and position of the substituted halogen atoms in halogenated semiconducting polymers impact, through self‐assembly modification, their optoelectronic properties in a way that is difficult to predict. Yet, the solid‐state self‐assembling of these materials has been shown to be a key parameter toward high charge transport properties and photovoltaic efficiencies. In this context, there is still a need to develop analytical methods that will enable an atomic‐scale structural characterization of these materials as a function of the halogenation. In this study, the solid‐state nuclear magnetic resonance (NMR) under magic angle spinning (MAS) is explored as a tool to investigate the local structure and supramolecular organization of a series of conjugated polymers, specially designed for this study. Through a comprehensive study using complementary techniques, including MAS–NMR, small and wide‐angle X‐ray scattering, and molecular modeling investigations, the molecular conformation of these polymers in relation to their chemical composition, is successfully determined.

Halogen atoms induced reversible supramolecular assembly and pH-response of the fluorescence properties: Low driving force triggered fluorescence switch with high SNR and high stability

With the aim to investigate the influence of halogens on electronic structures and fluorescence properties, a new Salen type hetero-halogenated lanthanide complex [CeIV((±)3Br5Cl-salmen)2] (Ce-χ-L) was synthesized, and a set of optical properties were investigated. The complex was characterized by FT-IR, elemental analysis, UV and single-crystal X-ray diffraction, and structural analysis revealed that halogen atoms plays a significant role in inducing the complex into a special intramolecular ‘X’ structure as well as supramolecular dimer assemblies. Theoretical calculations revealed that the introduction of halogen atoms is important for lowering the energy level of HOMO-LUMO the lanthanide complexes Schiff base complexes and also increase pathways of intermolecular interactions. pH stability test revealed the supramolecular assemblies of Ce-χ-L is sensitive to the variation of pH environment, and the accompanied assemble and disassemble behaviors are closely related to the substitution of halogen atoms.

Mesophase behaviour of 1,2,3-triazole-based nematic liquid crystals influenced by varying alkyl chains and halogen atom substitution

ABSTRACT To develop novel nematic-phase liquid-crystal (LC) materials with practical potential in optical and photovoltaic devices, the alkyl chain and halogen atom substitution in 1,2,3-triazole-based compounds were varied, and the effects on the mesophase behaviour were investigated. The 4-(4-propylcyclohexyl)phenyl 4-(1-alkyl-5-hydro/halo-1,2,3-triazol-4-yl)benzoate series 1 was successfully synthesised through tandem aerobic oxidative halogenation and click reaction via in situ activation. Except for 5-thiophene-1,2,3-triazole compound 1c-Th displaying no mesomorphism, the other compounds 1 form enantiotropic nematic mesophases, among which compounds 5-hydro-1,2,3-triazole 1c-H (C10) and 1d-H (C12) (long straight chain compounds) form two mesophases (smectic C phase and nematic phase). For 5-halo-1,2,3-triazole compounds 1c-X (× = halide), the mesomorphic temperature range was wider than for the corresponding compound 1c-H because of the effect of the halogen atom substituent on the triazole. Density functional theory (DFT) analysis showed that the structure-property relation for series 1c-X(H) could be defined by using the calculated dihedral angles, dipole moment, polarisability, and molecular electrostatic potential as parameters. Notably, introducing halogen atoms at the 5-position of 1,2,3-triazole can greatly broaden the mesogenic temperature range, ascribed to the weak intermolecular forces and large dipole moment in this class of compounds.

Advantage of Using NaH2PO2 over Alkali Metal Formates as a Hydrogen Source for Pd‐gC3N4 Catalyzed Hydro‐Dehalogenation of Aryl Halides

AbstractHalogenated and polyhalogenated aromatic compounds are known for their toxicity and effect on human health and the environment. These aromatic hydrocarbons have been widely used in pesticides, flame retardants, pharmaceuticals, and other industrial chemicals. The substitution of halogen atoms of aromatic halides by hydrogen atoms in the presence of a metal catalyst is an important organic transformation and is known as a catalytic hydro‐dehalogenation reaction. It is an important technique used for the treatment of halogenated industrial waste. Herein, we investigated the comparative hydro‐dehalogenation of aryl halides in the presence of Pd‐gC3N4 catalyst using various hydrogen transfer sources in an eco‐friendly manner. We also investigated the advantage of using sodium hypophosphite (NaH2PO2) as a hydrogen source for hydro‐dehalogenation in comparison to alkali metal formates. For hydro‐dehalogenation of 1 mmol of aryl halide, 2 equivalents of NaH2PO2 are used while 4 equivalents of KHCO2 are required in the presence of 3.8 wt % of Pd metal catalyst. The Pd‐GCN catalyst was characterized by various microscopic and spectral techniques such as PXRD, FTIR, SEM, TEM, XPS, and TGA, etc. A gram scale reaction was performed to analyze the industrial potential of the proposed catalytic system. Finally, the recyclability of Pd‐GCN was found excellent and the catalyst could run multiple cycles with sustained activity.

Toxicity of 17 Disinfection By-products to Different Trophic Levels of Aquatic Organisms: Ecological Risks and Mechanisms.

Intensified disinfection of wastewater during the COVID-19 pandemic increased the release of toxic disinfection by-products (DBPs). However, studies relating to the ecological impacts of DBPs on the aquatic environment remain insufficient. In this study, we comparatively investigated the toxicities and ecological risks of 17 typical, halogenated DBPs to three trophic levels of organisms in the freshwater ecosystem, including phytoplankton (Scenedesmus sp.), zooplankton (Daphnia magna), and fish (Danio rerio). Toxicity of DBPs was found to be species-specific: Scenedesmus sp. was the most sensitive to haloacetic acids, while D. magna was the most sensitive to haloacetonitriles and trihalomethanes. Specific to each DBP, toxicities were also related to their classes and substituted halogen atoms. Damage to photosystems and oxidative stress served as the potential mechanisms for DBPs toxicity to microalgae. The different sensitivities to DBPs indicate that a battery of bioassays with organisms at different trophic levels is necessary to determine the ecotoxicity of DBPs. Furthermore, the ecological risks of DBPs were assessed by calculating the risk quotients (RQs) based on toxicity data from multiple bioassays. The cumulative RQs of DBPs to all the organisms were greater than 1.0, indicating high ecological risks of DBPs in wastewater effluents.

Tuning the activity of known drugs via the introduction of halogen atoms, a case study of SERT ligands - Fluoxetine and fluvoxamine.

The selective serotonin reuptake inhibitors (SSRIs), acting at the serotonin transporter (SERT), are one of the most widely prescribed antidepressant medications. All five approved SSRIs possess either fluorine or chlorine atoms, and there is a limited number of reports describing their analogs with heavier halogens, i.e., bromine and iodine. To elucidate the role of halogen atoms in the binding of SSRIs to SERT, we designed a series of 22 fluoxetine and fluvoxamine analogs substituted with fluorine, chlorine, bromine, and iodine atoms, differently arranged on the phenyl ring. The obtained biological activity data, supported by a thorough in silico binding mode analysis, allowed the identification of two partners for halogen bond interactions: the backbone carbonyl oxygen atoms of E493 and T497. Additionally, compounds with heavier halogen atoms were found to bind with the SERT via a distinctly different binding mode, a result not presented elsewhere. The subsequent analysis of the prepared XSAR sets showed that E493 and T497 participated in the largest number of formed halogen bonds. The XSAR library analysis led to the synthesis of two of the most active compounds (3,4-diCl-fluoxetine 42, SERT Ki=5nM and 3,4-diCl-fluvoxamine 46, SERT Ki=9nM, fluoxetine SERT Ki=31nM, fluvoxamine SERT Ki=458nM). We present an example of the successful use of a rational methodology to analyze binding and design more active compounds by halogen atom introduction. 'XSAR library analysis', a new tool in medicinal chemistry, was instrumental in identifying optimal halogen atom substitution.

Influence of halogen atom substitution and neutral HCN/anion CN- Lewis base on the triel-bonding interactions.

Triel-bonding interactions composed of Lewis acid TrOHH2/TrOH2X/TrOHX2 (Tr = B, Al, Ga; X = F, Cl, Br) molecule and Lewis base neutral HCN or anionic CN- molecule are of research significance in bond properties, which has been investigated at MP2/aug-cc-pVTZ theory level. It is also feasible to study the halogen atom substituent effect and influence of different Lewis bases on the formation of triel bond. AIM analyses reveal that Tr (Tr = B, Al, Ga)···N bond critical point (BCP) exists in all studied triel bond. In the formation of triel bonding, compared with Lewis base HCN molecule, Lewis base anionic CN- can participate in a stronger triel bond. Specifically, the structural change, deformation energy, and charge transfer of CN- complexes are all larger than that of HCN complexes. In addition, halogen atom substitution effect is also discussed. MEP value and binding energy of HCN and CN- complexes all increase after replacing one or two hydrogen atoms by halogen atoms (F, Cl, Br) in Lewis acid. Especially, replacing two hydrogen atoms by halogen atoms in Lewis acid has more remarkable enhancement in MEP value and binding energy than that of replacing only one hydrogen atom. After replacement, binding energy can be increased by 21.77kcal/mol. The neutral and anionic triel-bonded complexes composed by Lewis acid TrOHH2/TrOH2X/TrOHX2 (Tr = B, Al, Ga; X = F, Cl, Br) with Lewis base HCN and CN- are systematically investigated at MP2/aug-cc-pVTZ level. The neutral (HCN) triel bonding is weaker than the anionic (CN-) triel bonding due to the smaller MEP value of the neutral HCN molecule. The replacement of hydrogens (-H) in Lewis acid by electron-withdrawing groups (-F, -Cl, -Br) has a prominent enhancement effect on the MEP value of π-hole and triel-bonding strength.

Halogenation Regulates Supramolecular Chirality at Hierarchical Levels of Self-Assembled N-Terminal Aromatic Amino Acids.

Halogenation brings about dramatic variations to the performance of self-assembled organic species, such as luminescence and crystallinity, but it has seldom been utilized for chirality control. Here we show the halogenation effect of self-assembling organic building units on supramolecular chirality and chiroptical responses. N-terminal aromatic amino acids with different substituted halogen atoms at p-phenylalanine residues self-assembled into one-dimensional fibrous structures. Halogenation induced the emergence of macroscopic chirality regardless of halogen properties like electronegativity, generating exclusive homochiral helical structures. Solid-state X-ray structures and time-dependent density functional theory were utilized for calculated electronic circular dichroism spectra, which evidenced the diverse driving forces to enable chiral molecular arrangements, including H-bonds and halogen bonds. Red-shifted luminescence was observed in brominated building units, giving rise to active circularly polarized luminescence. This work elucidates the multiple roles of halogen in chiral self-assembly systems, which provides insight into the rational control over supramolecular chirality and their chiroptical applications.

Optoelectronic and elastic properties of metal halides double perovskites Cs2InBiX6 (X = F, Cl, Br, I)

Structural geometry, electronic band gaps, density of states, optical and mechanical properties of double perovskite halides Cs2InBiX6 (X = F, Cl, Br, I) are investigated using the density functional theory. These compounds possess genuine perovskite stoichiometry, evaluated using various geometry-based indices like tolerance factor, octahedral factor, and formation energy. The fundamental electronic band gaps are direct and valued in the range 0.80–2.79 eV. These compounds have narrow band gaps (except Cs2InBiF6) due to strong orbital coupling of the cations. The valence band maximum and conduction band minimum are confirmed to be essentially of In 5s and Bi 6p characters, respectively. The splitting of Bi 6p bands due to strong spin-orbit coupling causes reduction in the band gaps. These compounds have large dispersion in their bands and very low carrier effective masses. The substitution of halogen atoms has great influence on the optical properties. The mechanical properties reveal that Cs2InBiX6 (X = F, Cl, Br, I) satisfy the stability criteria in cubic structures.

Novel copper(II) and zinc(II) complexes of halogenated bidentate N,O-donor Schiff base ligands: Synthesis, characterization, crystal structures, DNA binding, molecular docking, DFT and TD-DFT computational studies

Eight novel complexes, including: [Cu(L1)2]: C1, [Cu(L2)2]: C2, [Cu(L3)2]: C3, [Cu(L4)2]: C4, [Zn(L1)2]: Z1, [Zn (L2)2]: Z2, [Zn (L3)2]: Z3, and [Zn (L4)2]: Z4, with four bidentate N,O-donor halogenated bis-Schiff base ligands (HL1: 4-Bromo-2-[(4-fluorophenylimino) methyl]phenol; HL2: 4-Bromo-2-[(4-chlorophenylimino)methyl]phenol; HL3: 4-Bromo-2-[(4-bromophenylimino) methyl]phenol; HL4: 4-Bromo-2-[(4- iodophenylimino)methyl]phenol) were synthesized and their structures were proved by SC-XRD, FT-IR, UV-Vis, and 1H NMR spectroscopic techniques. The single crystal X-ray diffraction analysis reveals that a distorted tetrahedral geometry is formed in zinc complex whereas a slightly distorted square planar geometry is formed in both copper(II) complexes of C3 and C4. Theoretical calculations of the complexes were carried out via DFT as well as TD-DFT using B3LYP method employing the Def2-TZVP basis set, where the calculation results are in accordance with the experimental results. NBO analysis has been used to elucidate charge transfer information of the Z1, C3 and C4 complexes. Moreover, interaction of ligands and complexes with FS-DNA was assessed using UV-Vis spectroscopy as well as molecular docking. The experimental and theoretical results reveal that the DNA-binding affinity of as-prepared complexes increases with decreasing in electronegativity of substituted halogen atom.

Two Orthogonal Halogen-Bonding Interactions Directed 2D Crystalline Supramolecular J-Dimer Lamellae.

Dye assemblies exhibit fascinating properties and performances, both of which depend critically on the mutual packing arrangement of dyes and on the supramolecular architecture. Herein, we engineered, for the first time, an intriguing chlorosome-mimetic 2D crystalline J-dimer lamellar structure based on halogenated dyes in aqueous media by employing two distinct orthogonal halogen-bonding (XB) interactions. As the only building motif, antiparallel J-dimer was formed and stabilized by single π-stacking and dual halogen⋅⋅⋅π interactions. With two substituted halogen atoms acting as XB donors and the other two acting as acceptors, the constituent J-dimer units were linked by quadruple highly-directional halogen⋅⋅⋅halogen interactions in a staggered manner, resulting in unique 2D lamellar dye assemblies. This work champions and advances halogen-bonding as a remarkably potent tool for engineering dye aggregates with a controlled molecular packing arrangement and supramolecular architecture.

Discovery of novel inhibitors of phosphodiesterase 4 with 1-phenyl-3,4-dihydroisoquinoline scaffold: Structure-based drug design and fragment identification.

Currently, it is in urgent need to develop novel selective PDE4 inhibitors with novel structural scaffolds to overcome the adverse effects and improve the efficacy. Novel 1-phenyl-3,4-dihydroisoquinoline amide derivatives were developed as potential PDE4 inhibitors based on the structure-based drug design and fragment identification strategy. A SARs analysis was performed in substituents attached in the C-3 side chain phenyl ring, indicating that the attachment of methoxy group or halogen atom substitution at the ortho-position of the phenyl ring was helpful to enhance both inhibitory activity toward PDE4B and selectivity. Compound 15 with excellent selectivity, exhibited the most potent inhibition in vitro and in vivo, which is a promising lead for development of a new class of selective PDE4 inhibitors.

Chemometric modeling to predict air half-life of persistent organic pollutants (POPs)

We have reported here a quantitative structure-property relationship (QSPR) model for prediction of air half-life of organic chemicals using a dataset of 302 diverse organic chemicals employing only two-dimensional descriptors with definite physicochemical meaning in order to avoid the computational complexity for higher dimensional molecular descriptors. The developed model was rigorously validated using the internationally accepted internal and external validation metrics. The final partial least squares (PLS) regression model obtained at three latent variables comprises six simple and interpretable 2D descriptors. The simple and highly robust model with good quality of predictions explains 66% for the variance of the training set (R2) (64% in terms of LOO variance (Q2)) and 76% for test set variance (R2pred) (prediction quality). This model might be applicable for data gap filling for determination of POPs in the environment, in case of new or untested chemicals falling within the applicability domain of the model. In general, the model indicates that the air half-life of organic chemicals increases with presence of H-bond acceptor atoms, number of halogen atoms and presence of the R—CH-X fragment and lipophilicity, and decreases with presence of a number of halogens on ring C(sp3) (substitution of halogen atoms on a ring).