Coordination Of Nitrogen Atom Research Articles

Crystal Structure of a Flexible Schiff Base Complex of Zn(II) [ZnL(4,4'-bipyridyl)](ClO4), HL = 2-((2-(2-(benzylamino)ethylamino)ethylimino)-methyl)phenol

The crystal structure of [ZnL(4,4′-bipyridyl)2](ClO4) (HL = 2-((2-(2-(benzylamino)ethylamino)ethylimino)methyl)-phenol) was determined by X-ray diffraction method. This complex crystallized in the monoclinic space group P21/c, with, a = 10.536(2), b = 12.172(2), c = 22.219(4)A, β= 99.330(3)°, Z = 4, V = 2811.5(10)A3, and R = 0.0417. Each ZnII ion completed a distorted square pyramidal coordination configuration by three N donor atoms and one phenolic O donor atom from the Schiff base ligand, and one N donor atom from 4,4′-bipy molecule. Hydrogen-bonding dimmers were formed between two adjacent complex molecules by hydrogen bonding between a bipy molecule and a coordinated nitrogen atom of another complex molecule.

One- and Two-Dimensional Coordination Polymers Constructed from Bicapped Keggin Mixed Molybdenum−Vanadium Heteropolyoxoanions and Polynuclear Copper(I) Clusters Bridged by Asymmetrical Bipyridine (2,4‘-bipy and 2,3‘-bipy) Ligands

Two novel trimetallic coordination polymers containing bridging bicapped Keggin mixed Mo/V polyoxoanions and asymmetrical aromatic amine bridging ligands 2,3‘-bipyridine (2,3‘-bipy) or 2,4‘-bipyridine (2,4‘-bipy), [CuI6(2,3‘-bipy)6(2,3‘-bipy-2‘-O)2][VIV2MoV5MoVI7O38(PO4)] [2,3‘-bipy-2‘-OH = 3-(pyridin-2-yl)pyridin-2-ol] (1) and [CuI5(2,4‘-bipy)6(OH)][PMoVI8VV3VIVO40(VIVO)2]·1.5H2O (2), have been prepared under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. Gillard type hydration for the 2,3‘-bipy ligand was observed during synthesis of 1, which happens on the 2‘-carbon atom rather than on the α-carbon atom of the coordinated nitrogen atom in the 2,3‘-bipy ligand. Complex 1 is constructed from an alternatively arranged bivanadyl capped α-Keggin polymolybdate anion [VIV2MoV5MoVI7O38(PO4)]4- and double 2,3‘-bipy ligand bridged trinuclear copper(I) cluster [CuI3(2,3‘-bipy)3(2,3‘-bipy-2‘-O)]2+, forming a one-dimensional (1D) ribbon structure. The two-dimensional (2D) extended layer structure of 2 is composed of another type of bicapped Keggin mixed molybdenum−vanadium polyoxoanion [PMoVI8VV3VIVO40(VIVO)2]4- and copper(I) coordination polymer cation chain [CuI5(2,4‘-bipy)6(OH)]4+; the latter consists of a 2,4‘-bipy ligand bridged hexanuclear copper(I) cluster [CuI5(2,4‘-bipy)6]5+ linked by double hydroxyl groups.

Crystal Structures of the NO and N2O4 Sorption Complexes of Fully Dehydrated Fully Cd2+-Exchanged Zeolite X (FAU): Coordination of Neutral NO and N2O4 to Cd2+

The structures of the nitric oxide and dinitrogen tetroxide sorption complexes of dehydrated fully Cd2+-exchanged zeolite X (FAU) have been determined using single-crystal X-ray diffraction in the cubic space group Fdm at 21(1) degrees C. Ion exchange was accomplished by allowing an aqueous stream 0.05 M in Cd2+ to flow past each crystal for 5 days. Each crystal was then dehydrated at 500 degrees C and 2 x 10(-6) Torr for 2 days, followed by exposure to 100 Torr of zeolitically dry NO or NO2/N2O4 gas. The structures were determined in these atmospheres. The unit cell constants at 21(1) degrees C are 24.877(2) A for the dark-yellow NO complex, |Cd46(NO)16|[Si100Al92O384]-FAU, and 24.735(2) A for the black N2O4 complex, |Cd46(N2O4)25.5|[Si100Al92O384]-FAU. The structure of the NO complex was refined to R1 = 0.072 and wR2 = 0.134. In this structure, Cd2+ ions occupy four crystallographic sites. Fifteen Cd2+ ions occupy site I (at the centers of the double 6-rings (D6Rs)), and one occupies site I' (in the sodalite cavity opposite a D6R). The remaining 30 Cd2+ ions occupy two different sites II (near 6-rings in the supercages): 16 coordinate to nitric oxide molecules and 14 do not. Sixteen NO molecules lie in the supercage where each interacts weakly with a Cd2+ ion: Cd-N = 2.57(22) A. The observed N-O bond distance is 1.28(25) A and Cd-N-O is 118(10) degrees. The structure of the N2O4 complex was refined to R1 = 0.084 and wR2 = 0.216. In this structure, Cd2+ ions occupy only three crystallographic sites. The 16 D6Rs per unit cell are filled with 11.5 Cd2+ ions at site I and 9 Cd2+ ions at site I': 11.5 + 9/2 = 16. The remaining 25.5 Cd2+ ions occupy site II where each coordinates at 2.43(8) A to a nitrogen atom of a N2O4 molecule. At the coordinating nitrogen atom, O-N-O is 147(10) degrees and the N-O bond lengths are 1.07(9) and 1.23(10) A. At the second nitrogen atom, O-N-O is 140(10) degrees, and the N-O bond lengths are 1.03(13) and 1.42(12) A. The imprecisely determined N-N bond length, 2.74(17) A, appears to be very much lengthened by coordination to Cd2+. The Cd-N-N angle is 144(10) degrees. This appears to be the first crystallographic report of the coordination of N2O4 to a cation.

Spectroscopy of europium and terbium pyridine-carboxylates

Luminescence, luminescence excitation, IR, and Raman spectra of europium and terbium isomeric pyridine-carboxylates: isonicotinates, nicotinates and picolinates were studied. The ways of the excitation energy transfer from the ligand to Ln3+ were analysed in dependence on the structure and the type of co-ordination of ligand. Intraligand charge transfer bands and Tb3+ f–d transition bands were identified in the luminescence excitation spectra of terbium and europium compounds. Co-ordination of nitrogen atom by terbium ion in picolinates (and dipicolinates) causes low-frequency shift of the f–d bands and promotes the excitation of luminescence through d-states of Tb3+.

Spectroscopy of europium and terbium pyridine-carboxylates

Luminescence, luminescence excitation, IR, and Raman spectra of europium and terbium isomeric pyridine-carboxylates: isonicotinates, nicotinates and picolinates were studied. The ways of the excitation energy transfer from the ligand to Ln 3+ were analysed in dependence on the structure and the type of co-ordination of ligand. Intraligand charge transfer bands and Tb 3+ f–d transition bands were identified in the luminescence excitation spectra of terbium and europium compounds. Co-ordination of nitrogen atom by terbium ion in picolinates (and dipicolinates) causes low-frequency shift of the f–d bands and promotes the excitation of luminescence through d-states of Tb 3+ .

Carbonic anhydrase inhibitors: X-ray crystallographic structure of the adduct of human isozyme II with EMATE, a dual inhibitor of carbonic anhydrases and steroid sulfatase

The X-ray crystal structure for the adduct of human carbonic anhydrase II (hCA II) with estrone-3- O-sulfamate (EMATE), an antiendocrine agent showing both CA and estrone sulfatase inhibitory properties, has been resolved at a resolution of 1.5 Å. Its binding to the enzyme is similar to that of other sulfamates/sulfonamides, considering the interactions of the zinc anchoring group, but differs considerably when the steroidal scaffold of the inhibitor is analyzed. This part of the inhibitor interacts only within the hydrophobic half of the CA active site, interacting with residues Val 121, Phe 131, Val 135 and Pro 202, and leaving the hydrophilic half able to accommodate several water molecules not present in the uncomplexed enzyme. In addition, a very short bond of 1.78 Å between the zinc ion and the coordinated nitrogen atom of the sulfamate moiety is observed, which may explain the high affinity of this inhibitor for hCA II ( K i of 10 nM).

Non-Linear Effects in Asymmetric Reactions: Negative and Positive Stereoselectivity in the Formation of Homoleptic 1:2 Metal to Ligand Complexes of Chiral 1,9-Disubstituted Semicorrin Ligands

The stereoselectivity of the formation of bis-chelates with the 1,9-disubstituted chiral semicorrin ligands (1S,9S)-dimethyl 5-cyanosemicorrin-1,9-dicarboxylate (1) for Co2+, Ni2+, Cu2+, and Pd2+ and with its (1S,9S)-diethyl analogue 2 for Co2+ and Cu2+ have been measured by the method of continuous variation of enantiomers, and with 1 for Zn2+ by NMR. Positive selectivities were found for Co2+, Ni2+, and Zn2+ complexes, whereas very high negative selectivities prevail in the complexes of Cu2+ and Pd2+. These results are rationalised by X-ray structural determinations of some of the corresponding complexes. The optically active Cu2+ and Pd2+ complexes show distorted square planar structures with chirality predetermined by the chirality of the ligand. Ni2+ complexes are five or hexacoordinated and exhibit a distorted tetrahedral arrangement of the four coordinated nitrogen atoms. In the optically active compound the ester moiety is coordinated by the oxygen atom of the alkoxy group and the arrangement of the two N-N chelate rings shows ?-(S,S) chirality. Interestingly, with the racemic ligand, it is not the more stable heterochiral, but the racemic complex containing the two homochiral enantiomers which is obtained. The coordination of the ester groups occurs by the carbonyl oxygen and the chirality is opposite to the optically active compound, e.g ?(S,S)/?-(R,R). The structure of the optically active zinc compound shows very weak interaction with the alkoxy group of one ester moiety of each ligand molecule and the chirality of the N-N-chelate rings is ?-(S,S). Again, the compound obtained with the racemic ligand contains the enantiomers of the homochiral complex, the chirality of which is ?-(R,R)/?-(S,S). The results are discussed with respect to the possibility to perform asymmetric amplifications of the 1:1 complexes of semicorrin ligands as enantioselective catalysts.

Note: Synthesis, Characterization and Crystal Structures of the Coordination Polymers [Cu(II)(NO3)2(BBMB) and [Mn(II)Cl2(BBMB)2] [BBMB = 1,4-Bis(1-Benzimidazolylmethyl) Benzene

Two novel coordination polymers, [Cu(II)(NO3)2(bbmb)] n (1) and [Mn(II)(Cl2)(BBMB)2] (2) [bbmb = 1,4-bis(1-benzimidazolylmethyl)benzene], were synthesized and characterized by IR and thermal analyses. Single-crystal X-ray diffraction analysis shows that Polymer 1 exhibits a distorted metal tetrahedron in its structure, involving two nitrogen atoms from bbmb ligands and two oxygen atoms from NO3 groups. Each Cu(II)(NO3)2 unit is bridged by bbmb to form a zigzag chain structure. Polymer 2 possesses a two-dimensional network. The coordination environment around Mn(II) is a distorted octahedron and its solid-state structure exhibits a layered packing mode. In the polymers the two coordinating nitrogen atoms on bridging bbmb ligands are trans to the central benzene plane.

Studies of Pyridinyl‐Containing 14‐Membered Macrocyclic Copper(II) Complexes

AbstractSix copper(II) complexes of tetracoordinating, pyridinyl‐containing 14‐membered macrocycles with varying ratios of nitrogen and oxygen donor atoms were prepared and characterized by IR, UV/Vis, and EPR spectroscopy and cyclic voltammetry. A distorted tetragonal coordination of the copper center in the solid‐state was established by X‐ray crystallography for the tetraazamacrocyclic complex Cu‐3 carrying a methoxybenzyl pendent arm and the trioxaaza complex Cu‐6. The superoxide dismutase‐like activity of the CuII complexes was investigated by inhibition of NADH oxidation. Although the UV/Vis and EPR spectra of the complexes were strongly affected when the coordinating nitrogen atoms were successively replaced by oxygen atoms, no significant change in their reactivity towards superoxide was observed. In all cases a 1:1 or 1:2 stoichiometry for the reaction with superoxide was found, with the exception of the methoxybenzyl‐substituted tetraaza complex, which showed a low catalytic activity with a turnover number of about 10. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Aminoallenylidene complexes of ruthenium(ii) from the regioselective addition of secondary amines to butatrienylidene intermediates: a combined experimental and theoretical study of the hindered rotation around the CN-bond

Aminoallenylidene complexes trans-[Cl(dppm)2RuC3(NRR′)(CH3)]+ are obtained from the regioselective addition of secondary amines to trans-[Cl(dppm)2RuCCCCH2]+. Unsymmetrically substituted amines give rise to Z/E isomeric mixtures. Dynamic 31P NMR spectroscopy gave an energy barrier of about 85 kJ mol−1 for rotation around the CN-bond pointing to a large contribution of the iminium alkynyl resonance form trans-[Cl(dppm)2Ru–CC–C(NRR′)(CH3)]+. This is also indicated by the pronounced bond length alternation within the RuC3N-chain as is revealed by X-ray structure analysis of the Z isomer of the (benzylmethyl)methylamine derivative 2d. The issue of NR2 rotation was also addressed by DFT calculations on the trans-[Cl(dhpm)2RuC3{N(CH3)2}(CH3)]+ model complex (dhpm = H2PCH2PH2). Upon rotation around the iminium type CN bond, the nitrogen lone pair and the π-system of the allenylidene ligand are decoupled, resulting in a significantly longer CN bond and a tetrahedrally coordinated nitrogen atom.

A donor–acceptor model of Ln(III) complexation with terdentate nitrogen planar ligands

The mechanism of the formation of a complex between several planar terdentate nitrogen ligands and trivalent lanthanides (Ln3+) in mixed MeOH–H2O solutions is studied and a model is proposed for the thermodynamic properties of the complexation reactions. The objective is not to cover all aspects of complexation between Ln3+ and planar terdendate nitrogen ligands, but rather to provide insight into the factors that govern the complexation mechanism. It is shown that the complexation of Ln3+ in solution with similar ligands does not follow the classical trends in change of thermodynamic properties across the Ln series, which have long been known. Ab initio calculations show that the stability of complexes increases with the increasing electron donor ability of the coordinating central nitrogen atom (Nc) of the ligand and the electron acceptor ability of the coordinating lateral ones (Nl). The effect of covalence for the stability of complexes is analysed. The complexes with high stability are characterised by distinct covalence of the bonds between Ln3+ and the lateral coordinating nitrogen atoms of the ligand. The thermodynamic properties of complexation of Ln3+ with 2,6-bis-(pyridin-2-yl)-4-amino-1,3,5-triazine (Adptz) and 2,6-bis-(1,2,4-triazin-yl)-pyridine (Btp) are compared. The central ring is negatively charged in the Adptz ligand, but positive in Btp. The strong donor–acceptor interaction and the net covalence result in an enthalpy mechanism of complexation of Ln3+ with Adptz. Owing to the repulsion between the cation and the central nitrogen atom in the [Ln(Btp)]3+solv complexes, the cation is pushed away from the nitrogen cavity, the Ln–Nc interatomic distances become larger and the electron donor ability of Nc is weak. Entropy promotes the formation of the [Ln(Btp)]3+solv complex.

Synthesis and characterization of a 1,8-difunctionalized dissymmetrical cyclam copper(II) complex bearing pyridylmethyl and N, N-dimethylcarbamoylmethyl groups

The new dissymmetrical ligand 1-( N, N-dimethylcarbamoylmethyl)-8-(2-pyridylmethyl)-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane, 5, was synthesized and the physicochemical properties of its copper(II) complex, [Cu II( 5)](ClO 4) 2·CH 3CN, were determined. UV–Vis, IR, ESR experiments, and X-ray analysis of [Cu II( 5)](ClO 4) 2·CH 3CN were carried out. The X-ray structure of [Cu II( 5)](ClO 4) 2·CH 3CN revealed a distorted square pyramid with the four coordinating nitrogen atoms of the macrocycle lying in the basal position. Curiously, the fifth ligand is the N, N-dimethylcarbamoylmethyl group through the oxygen atom and not the pyridylmethyl moiety.

Small heterocyclic ligands improve the copper-catalyzed oxidative coupling of 2,6-dimethylphenol to poly(2,6-dimethyl-1,4-phenylene ether)

Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) [J. Polym. Sci. A 36 (1998) 505], which is widely used in high-performance engineering plastics, is obtained by the copper-catalyzed oxidative coupling of 2,6-dimethylphenol. The oxidative polymerizations have been carried out in acetonitrile with copper-imidazole complexes as the catalyst precursor compounds, which appeared to be extremely active. Different substituents on the imidazole ring showed that both the ligand basicity and the steric hindrance close to the coordinated nitrogen atom are important factors to increase the catalytic activity. Higher activities are always found with an excess of ligand and when using monodentate ligands instead of didentate ones. Most likely, the imidazole moieties may also act as base. Another nitrogen donor ligand, viz. 2-methyl-oxazoline, has been successfully tested, showing a very good activity in this oxidative coupling reaction.

Powder Synthesis and Characterization of Amorphous Carbon Nitride

Carbon nitride powder prepared by solid-state reaction between cyanuric chloride or its fluoro analogue and lithium nitride. The determined, by elemental analysis, atomic N/C ratio (1.33) in the synthesized material is consistent with C 3 N 4 stoichiometry. Combined material characterization data, obtained by FTIR, Raman, UV-Vis, (13C) MAS NMR, XPS, TGA/DTA and pyrolysis-EIMS methods, provide substantial evidence for graphite-like sp 2 -bonded structure composed of building blocks of s-triazine rings bridged by the three-fold coordinated nitrogen atoms in the bulk carbon nitride.

Interpretation of the EPR Spectra of Nitrogen-Containing Compounds Adsorbed on Copper-Exchanged Zeolites

Electron paramagnetic resonance (EPR) spectroscopy was used to investigate adsorption of a series of amines (ammonia, methylamine, triethylamine) on Cu−ZSM5 and Cu−Beta. Several changes were observed in the EPR spectra after adsorption of the amine: an increase in spectral broadening, a shift in the copper hyperfine features, and the appearance of nitrogen hyperfine splittings in the perpendicular region of the EPR spectrum for some of the samples. For samples that exhibited resolved nitrogen hyperfine couplings, the EPR spectra were easily interpreted in terms of the number of coordinated amine molecules. For samples in which resolved nitrogen hyperfine interactions were not observed, the interpretation of the EPR spectrum was more complex. A second approach for the interpretation of the EPR spectrum involved using an empirical model correlating the EPR parameters for a series of model compounds to the number of coordinated nitrogen atoms and the charge of the copper complex. This approach was very useful for determining the number of coordinated nitrogen atoms if the charge of the complex was known or vice versa. It was determined that four molecules of ammonia or methylamine bind to the Cu2+ centers in Cu−ZSM5 and Cu−Beta, but that only one molecule of triethylamine is able to bind to the Cu2+ centers in these zeolites. For cases in which the charge of the complex and the number of ligands are both unknown, there is more uncertainty in using this empirical approach to interpret the EPR spectra. This empirical approach was further assessed by application to the EPR spectra of NO adsorbed on Cu−ZSM5 and Cu−Beta.

Cyclic voltammetry study of the electrocatalysis of carbon dioxide reduction by bis(polyazamacrocyclic) nickel complexes

Two series of binuclear macrocyclic nickel(II) complexes with varying lengths of the chain linking the two macrocyclic rings were characterised by cyclic voltammetry under argon and CO 2. The first series consisted of binuclear complexes [Ni 2L 2–6] 4+ containing pentaaza macrocycles with (CH 2) n bridges ( n=2, 3, 4, 6) or a p-xylyl linkage (L 6). In general, the two nickel sites in the binuclear complexes behave independently with the currents corresponding to the simultaneous transfer of two electrons. The redox potentials are remarkably constant along this series, but the peak separations increase, reflecting slower electron transfer due to more effective adsorption on the electrode. Electrochemical data for the electrocatalytic reduction of CO 2 in MeCN/10% H 2O revealed catalytic waves for CO 2 reduction with E p c close to −1.7 V and catalytic currents ( i p c) which are about half those of the mononuclear complex, proposed to be due to steric constraints allowing strong interaction of only one nickel centre of the binuclear one on the surface. The catalytic currents increased slightly as the linking chain length increased as the stereochemical constrains were relaxed somewhat. There was also a splitting in the catalytic peaks of the bismacrocyclic complexes which could reflect two types of adsorbed catalyst sites. In the more sterically crowded series of complex, [Ni 2L 7] 4+ along with the series of linked heptaaza macrocyclic complexes [Ni 2L 9–11] 4+ much more positive redox potentials were observed due to both alkylation of the coordinated nitrogen atoms, which decreases the ligand field, and the introduction of steric barriers to axial coordination. These steric barriers prevented strong electrode interaction and led to a lower catalytic activity. Indeed, the complex [Ni 2L 7] 4+ did not even show any interaction with CO 2 in dry acetonitrile. The complexes showed well separated peaks due to solution and surface catalytic activity, and the surface catalytic currents were now comparable to mononuclear complexes at the same effective concentration. We proposed that the less effective absorption on the electrode arising from ligand steric interactions places far fewer stereochemical constraints on the adsorption of both nickel centres to the same extent as the binuclear complex, and hence the catalytic currents for binuclear complex and mononuclear complex are comparable.

Polyphosphazene Electrolytes. 2. Synthesis and Properties of New Polymer Electrolytes Based on Poly((amino)[(2-methoxyethoxy)ethoxy])phosphazenes

A series of ether group and amino group cosubstitutent phosphazene copolymers was synthesized and characterized by a combination of NMR, elemental analysis, and FTIR spectroscopy. The length of the alkyl group in the amino side chain and the content of the methoxyethoxyethoxy (MEE) substituent on the polymer properties were varied. Dynamic mechanical analysis (DMA) demonstrated that the cosubstitutent polymers prepared have better mechanical properties than the ether homopolyphosphazene, poly[bis(2-methoxyethoxy)ethoxy]phosphazene, MEEP. The copolymers that possessed multiple electron-donor coordination sites, nitrogen and oxygen atoms, were complexed with various amounts of lithium perchlorate (LiClO4) to form polymer electrolytes. The ionic conductivity of the polymer electrolytes were determined by an impedance analyzer in a temperature range of 30−80 °C. According to those results, the conductivities of the prepared polymer electrolytes increased according to the rise in the MEE side chain contents and reached optima at F = 0.2−0.25. The best conductivity obtained is 2.2 × 10-5 S/cm for CPE-3A with F = 0.25.

Studies of Metal Complexes of 2-(2-Pyridinyl)-, 2-(6-Methyl-2-Pyridinyl)-, 2(3Pyridinyl)-1H-Benzimidazoles with Some D8–10 Ions

2-R-lH-Benzimidazoles [L1, R = 2-pyridinyl; L2, R = 6-methyl-2-pyridinyl; L3, R = 3-pyridinyl] and their complexes with Ni(II), Pd(II), Zn(II), Cd(II), Hg(II) chloride were prepared. The complexes, having 1:1 and 1:2 metal:ligand ratios, were characterized by elemental analyses, magnetic susceptibility and molar conductance measurements, IR and 1H NMR spectroscopy. The Ni(II) complexes are paramagnetic. The metal:ligand ratio are 1:1 in the Pd(II) and Hg(II) complexes of the ligands, and these complexes are non-ionic. In the IR spectra the band character and vibratioual frequencies of the groups participating in coordination changed on complexation. In the 1H NMR spectra, considerable changes were found in the chemical shifts of protons neighboring to the coordinated nitrogen atoms. The ligands L1 and L2 give chelates easily with the metal ions, but L3 does not.

Two-fold coordinated nitrogen atom: an electron trap in MOS devices with silicon oxynitride as the gate dielectric

Having conducted semiempirical quantum-chemical simulation (MINDO/3) of several clusters at different charge states, we identify that the two-fold coordinated nitrogen atom with an un-paired electron (Si 2N·) is the most responsible trap center for the observation of large electronic capturing in SiO xN y. Our calculations also show that electron localized in this defect will result in spin dissipation. Trap formation and removal mechanisms during nitridation and re-oxidation are also discussed in this work.

Capturing Properties of Two-Fold Coordinated Nitrogen Atom in Silicon Oxynitride

ABSTRACTElectronic structure of two-fold coordinated nitrogen atom ≡Si2N• in Si3N4 and SiOxNy is studied in different charged states by the semiempirical quantum-chemical method MINDO/3 taking into account an atomic relaxation. It is shown theoretically that the neutral paramagnetic defect ≡Si2N• captures an electron, therefore it is an electron trap in Si3N4 and SiOxNy. The calculations show that the capturing of hole by the ≡Si2N• defect can be energetically favorable only for large oxygen concentration in oxynitride. It is predicted that the electron localization by the ≡Si2N• defect will result in the ESR signal disappearance.