Nontemplate Synthesis of Two Novel 23-Membered N3O4-Donor Macrocycles

Abstract

A novel 23-membered heptadentate N₃O₄ Schiff base ligand has been prepared by [1 + 1] cyclocondensation of 1,2-bis(2′-aminophenoxy)-4-t-butylbenzene with 2,6-bis(2-formylphenoxymethyl)pyridine by a nontemplate procedure. Treatment of L₁ with NaBH₄ in EtOH/CHCl₃ gave the di-amine macrocycle L_2.     

Two new Keggin-type polyoxometalate-based organic-inorganic hybrid compounds with metal ions and chelate ligands

Two new hybrid compounds with chemical formulas [Co(L₁)₂(H₂O)₂]₂[SiW₁₂O₄₀]·6H₂O (1) and [Cu₂(C₉H₂₂ N)₂(L₂)₂][SiW₁₂O₄₀]·2H₂O (2) (L₁ = 3,3′-diamino-5,5′-bis(1H-1,2,4-triazole), L₂ = 1,2-bis(3-(2-pyridyl)pyrazole-1-ylmethyl)benzene, C₉H₂₂ N = tripropylamine) were prepared in a hydrothermal reaction system containing Keggin-type polyoxometalates (POMs), transition metal (TM) salts (cobalt salts and copper salts), and chelate L₁/L₂ ligands. X-ray structural analysis reveals that 1 and 2 possess 3-D supramolecular host frameworks with large cavities and the polyoxoanions SiW₁₂ reside in these cavities as the guest templates. The photocatalytic activities of 1 and 2 were investigated. Both compounds show efficient catalytic activity for degradation of RhB with 1 > 2. The loading amount of the POM units and the structural features of these POM-based organic-inorganic hybrid compounds may be necessary factors that affect the activity of catalysts in the photocatalytic degradation.     

Spacers-directed structural diversity of Co(II)/Zn(II) complexes based on S-/O-bridged dipyridylamides: electrochemical,fluorescent recognition behavior and photocatalytic properties

To investigate the effect of the spacers of S-/O-bridged dipyridylamides on the structures of Co(II)/Zn(II) complexes, [Co(L¹)(chda)]·1.5H₂O (CP1), [Co(L²)(chda)] (CP2), [Zn(L¹)(hip)]·DMA·2H₂O (CP3), and [Zn(L²)(hip)]·2.8H₂O (CP4) [L¹ = N,N′-bis(pyridine-3-yl)thiophene-2,5-dicarboxamide, H₂chda = trans-1,4-cyclohexanedicarboxylic acid, L² = N,N′-bis(pyridine-3-yl)-4,4′-oxybis(benzoic) dicarboxamide, H₂hip = 5-hydroxyisophthalic acid, DMA = N,N-dimethylacetamide], have been solvothermally synthesized. X-ray single-crystal diffraction shows that CP1 is a 2-D 3,5-connected network based on Co-L¹ linear chains and (Co-chda)₂ double chains. CP2 features a 1-D structure derived from 1-D wave-like (Co-chda)₂ double chains decorated by terminal L² ligands. CP3 and CP4 show wave-like (4,4) networks constructed by 1-D Zn-L¹ zigzag and Zn-hip zigzag (for CP3)/linear (for CP4) chains. The effect of the spacers of S-/O-bridged dipyridylamides on the structures of the title complexes was discussed. Electrochemical behaviors of CP1–CP2 and solid-state luminescent properties of CP3–CP4 were studied. The luminescence investigations show that CP3 and CP4 are recycled fluorescent probes for environmentally relevant Fe³⁺ ions. The photocatalytic properties for the degradation of methylene blue (MB) under ultraviolet light irradiation of CP3–CP4 and the recyclable materials after fluorescent sensing Fe³⁺ ions (named CP3@Fe³⁺ and CP4@Fe³⁺) have also been investigated.     

A bi-chain CoII coordination framework bridged by water molecules: magnetic properties and photocatalytic behavior

A new coordination framework, [Co₂(L)₂(bpy)₂(H₂O)]_n (1) (H₂L = (4-phenyl)-2,6-bis(4-carboxyphenyl)pyridine and bpy = 2,2′-bipyridine), has been prepared and structurally characterized. Complex 1 shows an interesting bi-chain substructure bridged by coordinated water molecules, which is further extended into a three-dimensional (3-D) supramolecular structure by π–π stacking interactions. Moreover, the magnetic properties and photocatalytic activity for degradation of methyl orange have been investigated.     

Vanadium complexes with quadridentate Schiff bases

The Schiff base ligands N,N′-(±)-trans-bis(3,5-dichloro-2-hydroxyacetophenone)-1,2-cyclohexanediamine (H₂L¹) and N,N′-(±)-trans-bis(5-chloro-4-methyl-2-hydroxyacetophenone)-1,2-cyclohexanediamine (H₂L²) were derived from the condensation of trans-1,2-diaminocyclohexane with 3,5-dichloro-2-hydroxyacetophenone or 5-chloro-4-methyl-2-hydroxyacetophenone, respectively. Both these ligands formed well-defined complexes with vanadium (IV) and (V) under suitable experimental conditions. These complexes have been characterized by elemental analysis, molar conductivity, magnetic moments, infrared, electronic spectra, ESR, X-ray diffraction, and thermogravimetric analysis. X-ray diffraction study of [VO(L²)]·H₂O complex indicated its monoclinic crystal system with a = 9.8525, b = 23.6271, c = 9.0904 Å, and β = 97.87°. The complexes [VO(L¹)]·H₂O and [VO(L²)]·H₂O have been examined as catalysts for epoxidation of styrene in the presence of hydrogen peroxide as oxidant. The IR spectral data suggest that both the ligands behave as dibasic tetradentate chelating agent with ONNO donor atoms sequence toward cental metal ion.     

Large branched alkylthienyl bridged naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole-containing low bandgap copolymers: Synthesis and photovoltaic application

Two donor-acceptor (D-A) type low bandgap (LBG) alternating conjugated copolymers containing larger conjugation planarity and stronger electro-withdrawing ability naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (NT) unit, namely, poly[4,8-bis(5-(n-octylthio)thien-2-yl)-benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-4,9-bis(4-(2-decyltetradecyl)thien-2-yl)naphtho- [1,2-c:5,6-c′]bis[1,2,5]thiadiazole-5,5′-diyl] (PBDT-TS-DTNT-DT) and poly[4,8-bis(triiso-propylsilylethynyl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-4,9-bis(4-(2-decyltetradecyl)-thien-2-yl)naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole-5,5′-diyl] (PBDT-TIPS-DTNT-DT), were prepared by the palladium-catalyzed Stille polycondensation and characterized by gel permeation chromatography (GPC), UV-Vis absorption, thermal gravimetric analysis (TGA), cyclic voltammetry (CV) etc. PBDT-TS-DTNT-DT and PBDT-TIPS-DTNT-DT show the broader absorption and deeper highest occupied molecular orbital (HOMO) energy level approximately ?5.45 and ?5.62 eV, respectively. Bulk-heterojuction solar cells based on the resulted polymers and [6,6] phenyl-C₆₁ butyric acid methyl ester (PC₆₁BM) blends, with the device configuration of ITO/PFN/polymer:PC₆₁BM/MoO₃/Ag were prepared and investigated. The results showed the power conversion efficiency (PCE) of 2.67% for PBDT-TS-DTNT-DT/PC₆₁BM (w:w, 1:2) and 0.64% for PBDT-TIPS-DTNT-DT/PC₆₁BM (w:w, 1:1), with relatively high open-circuit voltage (V_OC) of 0.86 and 1.05 V, small short-circuit current (J_SC) of 5.41 and 0.97 mA cm^?2 and moderate fill factor (FF) of 57.8% and 62.4%, under an AM1.5 simulator (100 mWcm^?2), respectively.     

In Situ Metal-Assisted Ligand Modification Induces Mn4 Cluster-to-Cluster Transformation: A Crystallography,Mass Spectrometry,and DFT Study

Dehydration of (S,S)-1,2-bis(1H-benzo[d]imidazol-2-yl)ethane-1,2-diol (H₄L) to (Z)-1,2-bis(1H-benzo[d]imidazol-2-yl)ethenol) (H₃L′) was found to be metal-assisted, occurs under solvothermal conditions (H₂O/CH₃OH), and leads to [Mn^II₄(H₃L)₄Cl₂]Cl₂ ⋅ 5 H₂O ⋅ 5 CH₃OH ( Mn₄L₄ ) and [Mn^II₄(H₂L′)₆(μ₃-OH)]Cl ⋅ 4 CH₃OH ⋅ H₂O ( Mn₄L′₆ ), respectively. Their structures were determined by single-crystal XRD. Extensive ESI-MS studies on solutions and solids of the reaction led to the proposal consisting of an initial stepwise assembly of Mn₄L₄ from the reactants via [MnL] and [Mn₂L₂] below 80 °C, and then disassembly to [MnL] and [MnL₂] followed by ligand modification before reassembly to Mn₄L′₆ via [MnL′], [MnL′₂], and [Mn₂L′₃] with increasing solvothermal temperature up to 140 °C. Identification of intermediates [Mn₄L_xL′_6−x] (x=5, 4, 3, 2, 1) in the process further suggested an assembly/disassembly/in situ reaction/reassembly transformation mechanism. These results not only reveal that multiple phase transformations are possible even though they were not realized in the crystalline state, but also help to better understand the complex transformation process between coordination clusters during “black-box” reactions.     

Two Zn(II) coordination polymers based on 1,3-di(4’-carboxyl-phenyl)benzene and N-donor coligands: syntheses,crystal structures,and luminescent properties

Two coordination polymers, {[Zn(dpb)(3-bpmp)_0.5]·1.5(DMF)}_n (1) and [Zn(dpb)(4-bpmp)]_n (2) (H₂dpb = 1,3-di(4′-carboxyl-phenyl)benzene, 3-bpmp = 1,4-bis(3-pyridylmethy)piperazine, 4-bpmp = 1,4-bis(4-pyridylmethy)piperazine and DMF = N,N-dimethylformamide), were solvothermally synthesized and characterized. Tuning the difference of N-donor ligands, we obtained 1 and 2 which display different topological nets. Complex 1 features a 6-connected topological net and 2 shows a 4-connected three-fold interpenetrated framework. Luminescent properties of 1 and 2 are investigated at room temperature.     

Catalytic oxyfunctionalization of saturated hydrocarbons by non-heme oxo-bridged diiron(III) complexes: role of acetic acid on oxidation reaction

Oxo-bridged diiron(III) complexes [Fe₂O(L¹)₂(H₂O)₂](ClO₄)₄ (1) and [Fe₂O(L²)₂(H₂O)₂](ClO₄)₄ (2), where L¹ and L² are tetradentate N-donor N,N′-bis(2-pyridylmethyl)-1,2-cyclohexanediamine and N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine respectively, have been isolated as synthetic models of non-heme iron oxygenases and characterized by physicochemical and spectroscopic methods. Both the complexes have been studied as catalysts for the oxyfunctionalization of saturated hydrocarbons using green hydrogen peroxide (H₂O₂) as oxidant under mild conditions. The selectivity (A/K) and regioselectivity (3°/2°) in oxidative C–H functionalization of alkanes suggests the involvement of metal-based intermediate in the oxygenation reaction. The catalytic efficiency is found to be strongly dependent on the presence of acetic acid. Remarkable increase in conversion and selectivity favoring the formation of alcohols in the oxidation of cyclohexane and cyclooctane and exclusive hydroxylation of adamantane with drastic enhancement of regioselectivity has been achieved by the addition of acetic acid in the presence of H₂O₂.

     

Silver(I) 3-D-supramolecular coordination frameworks constructed by the combination of coordination bonds and supramolecular interactions

Room temperature reactions of the ternary adducts of AgNO₃, bipodal ligand [4,4′-bipyridine (4,4′-bpy) or trans-1,2-bis(4-pyridyl)ethylene (tbpe) or 1,2-bis(4-pyridyl)ethane (bpe)] and organic ligand [4-aminobenzoic acid (4-aba) or 4-hydroxybenzoic acid (4-hba) or terephthalate ion (tph)] afford new 3-D supramolecular coordination polymers (SCPs), namely, {[Ag(4,4′-bpy) · H₂O](4-ab) · 2H₂O} (1), {[Ag(tbpe)]0.5(4-hb) · 3H₂O} (2), [Ag₂(L)₂ · (tph)] (L = 4,4′-bpy, tbpe) (3,4) and {[Ag₂(bpe)₂ · (tph)] · 2H₂O} (5). The bipodal ligand coordinates to silver forming a 1-D cationic chain (A), while the organic ligand and solvent form a 1-D anionic chain (B) via hydrogen bonds. The chains construct layers which are connected via hydrogen bonds and π–π stacking forming a 3-D network structure. The presence of the carboxylate, amino and hydroxyl groups in the organic ligands significantly extend the dimensionality via hydrogen bonds. All the SCPs 1–5 exhibit strong luminescence.     

Syntheses,crystal structures,and fluorescent properties of two Cd(II) complexes based on 2,2′-(ethane-1,2-diyl)bis(1H-imidazole-4,5-dicarboxylic acid)

Two new complexes, [Cd₂(H₄ebidc)₂(CH₃OH)₄]?·?2CH₃OH (1) and {[Cd(Cl)(I)(H₆ebidc)_1/2]?·?1/2bbe?·?H₂O} _n (2) (H₆ebidc?=?2,2′-(ethane-1,2-diyl)bis(1H-imidazole-4,5-dicarboxylic acid), bbe?=?1,2-bis(2-benzimidazolyl)ethane), are obtained through self-assembly of H₆ebidc with Cd(II). Single-crystal X-ray diffraction shows that 1 has a binuclear structure and each tridentate chelating ligand coordinates to two Cd(II) ions with µ₂-O. Complex 2 displays a 1-D chain structure and each tetradentate ligand bridges two Cd(II) ions in chelating fashion. Fluorescent properties have also been determined.     

Studies on mono- and dinuclear bisoxime copper complexes with different coordination geometries

Two new mono- and dinuclear Cu(II) complexes, namely [CuL¹]·0.5H₂O (1) and [(Cu₂(L²)₂)(DMF)]·0.5DMF (2) (H₂L¹ = 1,2-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)]methylene-aminooxy}ethane; H₂L² = 1,3-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)] methyleneaminooxy}propane), have been synthesized and characterized by X-ray crystallography. The unit cell of complex 1 contains two crystallographically independent but chemically identical [CuL¹] molecules and one crystalline water molecule, showing a slightly distorted square-planar coordination geometry and forming a wave-like pattern running along the a-axis via hydrogen bonding and π···π stacking interactions. Complex 2 has a dinuclear structure, comprising two Cu(II) atoms, two completely deprotonated phenolate bisoxime (L²)²⁻ moieties (in the form of enol), and both coordinated and hemi-crystalline DMF molecules. Complex 2 has square-planar and square-pyramidal geometries around the two copper centers, whose basic coordination planes are almost perpendicular and form an infinite three-dimensional supramolecular network structure involving intermolecular C–H···N, C–H···O, and C–H···π(Ph) hydrogen bonding and π···π stacking interactions of neighboring pyrazole rings.     

SYNTHESIS AND COMPLEX FORMATION OF NOVEL 12-MEMBERED MACROCYCLIC (E,E)-DIOXIMES

Abstract

Dibenzo[e,k]-2,3-bis(hydroxyimino) 1.4.7.10-tetrathia-2,3,8,9-tetrahydrocyclododecine (S₄H₂) and dibenzo-[e,k]-2,3-bis(hydroxyimino)-1,4-dithia-7,10-dioxa-2,3,8,9- tetrahydrocyclododecine (O₂S₂H₂) have been prepared from (E,E)-dichloroglyoxime, 2,3,8,9-dibenzo-1,4,7,10-tetrathiadecane (DTT) and 2,3,8,9-Dibenzo-4,7-dioxa-1,10-dithiadecane (DDD) which was synthesized by treating 1,2-bis(o-aminophenoxy)ethane with HNO₂ and potassium ethylxsanthate. The structures of these vic-dioximes have been determined as the (E,E)-forms according to ¹H-NMR and IR data. Only mononuclear complexes with a metal-ligand ratio of 1:2 have been isolated with Co(II), such as [(S₄H)₂Co(III)L′Cl] and [(O₂S₂H)₂Co(III)L′Cl]; Cu(II) forms only trinuclear complexes. Reaction of the mononuclear complexes with Pd(II) gives heterotrinuclear complexes.     

Design and syntheses of two threefold interpenetrating 2-D networks

Two new interpenetrating networks, [Ni(2,2′-bpy)(5-npa)(bpe)_0.5(H₂O)] _n (1) and [Ni(2,2′-bpy)(5-npa)(bpa)_0.5(H₂O)] _n (2) (2,2′-bpy?=?2,2′-bipyridine, 5-npa?=?5-nitroisophthalato, bpe?=?1,2-bis(4-pyridyl)ethylene, bpa?=?1,2-bis(4-pyridyl)ethane), have been synthesized and characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, X-ray powder diffraction, and single-crystal X-ray diffraction. Complexes 1 and 2 have similar structures and show a threefold interpenetrating topology constructed by three 2-D wave-like networks. Secondary building unit (SBU), [Ni(2,2′-bpy)(5-npa)(H₂O)] _n , was used as starting material of the multistep reaction. Replacing one coordination bond of chelating carboxyl group of SBUs by bpe and bpa afford the two threefold interpenetrating complexes.     

Synthesis,crystal structures,and catalytic properties of phenoxo-bridged dinuclear manganese(III) complexes with bis-Schiff bases

Two structurally similar centrosymmetric phenoxo-bridged dinuclear manganese(III) complexes, [Mn₂(L¹)₂(N₃)₂] (1) and [Mn₂(L²)₂(NCS)₂] (2), were prepared from the tetradentate bis-Schiff base ligands, N,N’-bis(salicylidene)propane-1,2-diamine (H₂L¹) and N,N’-bis(salicylidene)ethane-1,2-diamine (H₂L²), respectively, in the presence of pseudohalides. The complexes have been characterized by FTIR, elemental analyses, and molar conductivity. Structures of the complexes have been confirmed by single-crystal X-ray determination. The bis-Schiff base ligands coordinate with Mn through their phenolate oxygen and imino nitrogen. Each Mn is an octahedral. The complexes showed that they exhibit high activity in catalytic olefin oxidation.     

Carboxylate-bridged copper(II) complexes: synthesis,crystal structures,and superoxide dismutase activity

Two copper(II) complexes, [Cu₂(μ-benzoato)(L¹)₂]NO₃·2H₂O (1) and [Cu₂(μ-succinato)(L²)₂(H₂O)]ClO₄ (2), have been synthesized, where L¹ = N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzoylhydrazone and L² = N′-[(E)-pyridin-2-ylmethylidene]benzoylhydrazone. These complexes were characterized including by single-crystal X-ray diffraction studies. The copper is five-coordinate in 1 while in 2 one copper is five-coordinate and the other is six-coordinate. Electrochemical behavior of these complexes was measured by cyclic voltammetry. The conproportionation equilibrium constants (K_con) for both complexes have been estimated. The superoxide dismutase (SOD) activities of 1 and 2 were measured by nitro blue tetrazolium assay. Complex 1 has better SOD activity than 2.     

Syntheses and crystal structures of two Co(II) coordination polymers based on 4,6-bis(4-methylbenzoyl)isophthalic acid and 4,4′-bipyridine

Two coordination complexes, [Co₂L₂(4,4′-bpy)₂(H₂O)₄]?·?6H₂O (1) and [CoL(4,4′-bpy)] (2) (H₂L?=?4,6-bis(4-methylbenzoyl)isophthalic acid and 4,4′-bpy?=?4,4′-bipyridine), have been synthesized with the same starting materials under conventional and hydrothermal condition, respectively. Their structures have been characterized by X-ray diffraction, elemental analysis, IR spectra, and thermogravimetric analysis. Complex 1 features a 2-D sheet structure (space group C2/c) with (4,4) grid units. The non-covalent interactions (O–H?·?·?·?O, C–H?·?·?·?π, and weak π??·?·?·?π interactions) extend 1 into a 3-D supramolecular network. Complex 2 displays a (3,5)-connected network (space group P 1) with a (4²?·?6)(4²?·?6⁸) topology.     

Supramolecular inclusion of a pillared double-layered host by an anion-directed second-sphere coordination

In this paper, we have illustrated the utilisation of a second-sphere coordination approach to construct supramolecular inclusion solids with varieties of guest molecules. A flexible molecule N,N,N′,N′-tetra-p-methylbenzyl-ethylenediamine (L1) bearing doubly protonated H-bond donors was designed, capable of forming N–H…Cl hydrogen bonds with a crystallographically unique chloride anion, to construct an anion-directed ligand. The pillared double-layered host framework was constructed by an anion-directed ligand and primary coordination sphere [CoCl₄]^2 ?  through weak C–H…Cl hydrogen-bonding interactions. A variety of guest molecules, such as p-anisaldehyde, 1,4-dimethoxy-2,5-bis(methoxymethyl)benzene, can be included, leading to the formation of novel supramolecular inclusion solids: [L1]·4[H]⁺·[CoCl₄]^2 ? ·2Cl^? ·1.5[C₈H₈O₂]·0.25[CH₃OH] (1) and [L1]·4[H]⁺·[CoCl₄]^2 ? ·2Cl^? ·1.5[C₁₂H₂₀O₄]·0.5[CH₃OH] (2).

We have presented herein the utilisation of a second-sphere coordination approach to construct supramolecular inclusion solids with a variety of guest molecules. A novel type of a pillared double-layered host framework was constructed by a second-sphere coordination between the anion-directed ligand (L1 = N,N,N′,N′-tetra-p-methylbenzyl-ethylenediamine) and [CoCl₄]^2 ?  through weak C–H…Cl hydrogen-bonding interaction, and a variety of guest molecules, such as p-anisaldehyde, 1,4-dimethoxy-2,5-bis(methoxymethyl)benzene, can be included, leading to the formation of supramolecular inclusion solids: [L1]·4[H]⁺·[CoCl₄]^2 ? ·2Cl^? ·1.5[C₈H₈O₂]·0.25[CH₃OH] (1) and [L1]·4[H]⁺·[CoCl₄]^2 ? ·2Cl^? ·1.5[C₁₂H₂₀O₄]·0.5[CH₃OH] (2)

     

Four silver-containing coordination polymers based on bis(imidazole) ligands

Four coordination polymers, [Ag(L¹)](m-Hbdc) (1), [Ag(L¹)]₂(p-bdc)?·?8H₂O (2), [Ag(Hbtc)(L¹)][Ag(L¹)]?·?2H₂O (3) and [Ag₂(L²)₂](OH-bdc)₂?·?4H₂O (4), where L¹?=?1,1′-(1,4-butanediyl)bis(imidazole), L²?=?1,2-bis(imidazol-1-ylmethyl)benzene, m-H₂bdc?=?1,3-benzenedicarboxylic acid, p-H₂bdc?=?1,4-benzenedicarboxylic acid, H₃btc?=?1,3,5-benzenetricarboxylic acid, and OH–H₂bdc?=?5-hydroxisophthalic acid, were synthesized under hydrothermal conditions. Compound 1 contains a–Ag-L¹–Ag-L¹–chain and a hydrogen-bonding interaction induced–(m-Hbdc)-(m-Hbdc)–chain. Compound 2 consists of two independent–Ag-L¹–Ag-L¹–chains. P-bdc anions are not coordinated. Hydrogen bonds form a 3D supramolecular structure. A novel (H₂O)₁₆ cluster is formed by lattice water molecules in 2. Compound 3 contains a–Ag-L¹–Ag-L¹–and a–Ag(Hbtc)-L¹–Ag(Hbtc)-L¹–chain. The packing diagram shows a 2D criss-cross supramolecular structure, with?π?···?π?and C–H ···?π?interactions stabilizing the framework. Compound 4 contains a [Ag₂(L²)₂]²⁺ dimer with hydrogen-bonding,?π?··· π, and Ag ··· O interactions forming a 3D supramolecular framework. The luminescent properties for these compounds in the solid state are discussed.