A unique metal-organic framework [Cd2（L）1.5（μ3-OH）（H2 O）2 ]·2H2 O（1, H2 L = 2,5-dibenzoylterephthalic acid） has been synthesized under hydrothermal conditions, and characterized by single-crystal X-ray d...A unique metal-organic framework [Cd2（L）1.5（μ3-OH）（H2 O）2 ]·2H2 O（1, H2 L = 2,5-dibenzoylterephthalic acid） has been synthesized under hydrothermal conditions, and characterized by single-crystal X-ray diffractions, elemental analyses, IR spectra and fluorescence spectrum. The compound is of triclinic system, space group P1, C33 H27 CdO14, Mr = 870.33, a = 12.2939（17）, b = 12.5135（9）, c = 13.2046（10）, α = 115.3190（10）, β = 96.9140（10）, γ = 109.7950（10）°, V = 1641.6（3）3, Z = 2, Dc = 1.761 g/cm3, F（000） = 862, μ（MoK） = 1.366 mm-1, Rint = 0.0148, R = 0.0240 and wR = 0.0639 for 5995 observed reflections with I 〉 2σ（I）. X-ray analysis shows that the title complex exhibits a 3D framework with（412·63） topology, in which the tetra-nuclear [Cd4（μ3-OH）2 ] clusters act as 6-connected nodes, and the L ligands can be simplified to be linear connectors. Moreover, the thermal stability and fluorescence have been studied in detail.展开更多
A new tetranuclear cluster [Co4（bm）6C12]＇（H20）2-（CH3OH） （1, Hbm is （1H-benzi- midazol-2-yl）-methanol） has been synthesized by solvothermal method and structurally determined by IR, elemental analysis, and s...A new tetranuclear cluster [Co4（bm）6C12]＇（H20）2-（CH3OH） （1, Hbm is （1H-benzi- midazol-2-yl）-methanol） has been synthesized by solvothermal method and structurally determined by IR, elemental analysis, and single-crystal X-ray diffraction. Complex 1 belongs to monoclinie space group P21/n with a = 21.1713（5）, b = 12.7948（3）, c = 24.0195（9） А, β = 95.309（3）°, V = 6478.6（3） A3, Z = 4, F（000） = 2568, Dc = 1.289 g.cm-3, Mr = 1257.63,μ= 9.096 mm-I, S = 1.000, the final R = 0.0861 and wR = 0.2552 for 4956 observed reflections with 1 〉 20（/）. Two connected face-sharing cubes are observed in the framework of 1, each with one vertex missing. Complex 1 forms a 2-D network through N-H...O hydrogen bonds. The apparent holes can be observed.展开更多
The cluster compound[Mo_4S_4(μ-O_2CC_5H_5)_2(dtp)_4](dtp=S_2P(OEt)_2)was obtained by the ligand substitution reaction of tetranuclear molybdenum cluster [Mo_4S_4(μ-dtp)_2(dtp)_4]in the mixed solvent of acetone,ethan...The cluster compound[Mo_4S_4(μ-O_2CC_5H_5)_2(dtp)_4](dtp=S_2P(OEt)_2)was obtained by the ligand substitution reaction of tetranuclear molybdenum cluster [Mo_4S_4(μ-dtp)_2(dtp)_4]in the mixed solvent of acetone,ethanol and water in the presence of C_6H_5CO_2Na.It is monoclinic and crystallizes in space group C2/c, Mr=1495.09,a=12.175(5),b=22.01(1),c=20.875(9),β=99.04(4)°;V=5575(5);Z=4; Dc=1.78g/cm^3.Final R factor is 0.066.The result reveals that the[Mo_4S_4]cluster core and t-(dtp)^(-1)ligands are retained and only μ-bridged(dtp)^(-1)ligands are substituted by(C_6H_5CO_2)^(-1)in the substitution reaction,thus producing the new title cluster compound,the structure of which contains two species of bidentate ligand.展开更多
The new cluster[Mo_4(μ_3-O)_2O_4Cl_2(o-CH_3C_6H_4COO)_6]has been prepared by the reaction of molybdenum pentachloride and o-methylbenzoic acid.The crystal and molecular structures were determined by the X-ray diffrac...The new cluster[Mo_4(μ_3-O)_2O_4Cl_2(o-CH_3C_6H_4COO)_6]has been prepared by the reaction of molybdenum pentachloride and o-methylbenzoic acid.The crystal and molecular structures were determined by the X-ray diffraction method.It crystallizes in the orthorhombic space group Pnna with cell parameters:Mr=1361.6,a=13.792(4), b=17.957(3),c=20.974(9) ,V=5194(2) ~3,Z=4,Dc=1.74/cm^3,F(OOO)=2704,μ(MoK ) =11.0/cm,R=0.074.展开更多
The self-assembly of clusters in inorganic systems is an interesting subject. The self-assembly of big molecules has been well established in biological systems. In addition, the coordination chemistry of metal-sulfur...The self-assembly of clusters in inorganic systems is an interesting subject. The self-assembly of big molecules has been well established in biological systems. In addition, the coordination chemistry of metal-sulfur-nitrogen cluster complexes has been a very active and attracting field for many years as a result of the novelty and versatility of the crystal structures and reactivities of such clusters, as well as their potential applications as the models for the active sites in non-heme proteins. At the same time, there is currently considerable interest in the formation of metal complexes with heterocyclic ligands because of the diverse characteristics of ligands and their consequential wide range of applications.展开更多
Two novel zinc（Ⅱ） coordination polymers, [Zn2（BCB）（CH3OH）（μ3-OH）]n（1） and {[Zn2（BCB）（μ3-OH）（H2O）2]·CH3OH}n （2）, have been constructed from 3,5-bis（2-carboxylphenoxy）benzoic acid（H3BCB） an...Two novel zinc（Ⅱ） coordination polymers, [Zn2（BCB）（CH3OH）（μ3-OH）]n（1） and {[Zn2（BCB）（μ3-OH）（H2O）2]·CH3OH}n （2）, have been constructed from 3,5-bis（2-carboxylphenoxy）benzoic acid（H3BCB） and characterized by elemental analysis（EA）, IR, powder X-ray diffraction（PXRD）, and thermogravimetric（TG） analyses. Structural analysis reveals that complexes 1 and 2 are both 1D polymeric chains with unprecedented tetranuclear {Zn4（COO）4（μ3-OH）2} clusters, which were further expanded into a 2D structure. Fluorescence measurements show that 1 and 2 have highly selective and sensitive detection of nitrobenzene.展开更多
2-(2,3-Dihydroxpropyliminomethyl)6-methoxyphenol(H3L), trimethylacetic acid(Hpiv), Gd(NO3)3·6 H2O and Co(NO3)2·6 H2O were reacted in Me OH to obtain a heterometallic tetranuclear cluster [Gd2Co2(L)2(μ3-OH)2...2-(2,3-Dihydroxpropyliminomethyl)6-methoxyphenol(H3L), trimethylacetic acid(Hpiv), Gd(NO3)3·6 H2O and Co(NO3)2·6 H2O were reacted in Me OH to obtain a heterometallic tetranuclear cluster [Gd2Co2(L)2(μ3-OH)2(piv)6]·2 Hpiv·2 CH3OH(1). X-ray crystallographic analysis reveals that compound 1 was found to be a butterfly heterometallic tetranuclear cluster. The crystal(C64H108Co2Gd2N2O28, Mr = 1785.88) belongs to the triclinic crystal system, space group P1 with a =11.9798(6), b = 12.0877(5), c = 15.0367(7) A, α = 67.320(4)°, β = 81.583(4)°, γ = 75.201(4)°, V =1939.62(18) A3, Z = 1, T = 293.15 K, R = 0.048 and w R = 0.144 for 16299 observed reflections with I > 2σ(I). In magnetization study, heterometallic 1 exhibits magnetocaloric effect(MCE) of 14.75 J·kg-1·K-1 at 2 K for ΔH = 5 T, while it does not show non-linear response of the ac-susceptibilities.展开更多
Two lanthanide-oxo-cluster polymers were synthesized by hydrothermal reaction using Ln_2O_3 as initial lanthanide materials：[Ln_4（SO_4）_4（OH）_4（H_2O）_7]·_4H_2O（Ln = Er 1,Ho 2）,and characterized by PXRD,I...Two lanthanide-oxo-cluster polymers were synthesized by hydrothermal reaction using Ln_2O_3 as initial lanthanide materials：[Ln_4（SO_4）_4（OH）_4（H_2O）_7]·_4H_2O（Ln = Er 1,Ho 2）,and characterized by PXRD,IR spectra,X-ray single-crystal diffraction,2D IR correlation spectra and UV-visible absorption spectra.Single-crystal X-ray analyses reveal that compounds 1 and 2 are isostructural,and they are both crystallized in the orthorhombic system Pccn space group.Compound 1 is a 3D lanthanide cluster polymer based on tetranuclear cubane-like [Er_4（μ_3-OH）_4]^8＋ cations and SO_4^2- anions.The overall structure of 1 can be assigned to 6-connected pcu-type topology with the point symbol of（4^12.6^3）.展开更多
通过改变溶剂热反应温度,合成了2个结构不同的镉配合物[Cd_2(H_2ppty)_2(SO_4)_2(H_2O)_2]·3H_2O(1)和[Cd_2(ppty)(SO_4)(H_2O)_2]_n(2)(H_2ppty=3,5-bis-(1H-pyrazol-3-yl)-[1,2,4]triazol-4-ylamine)。进一步的研究表明,1和2的...通过改变溶剂热反应温度,合成了2个结构不同的镉配合物[Cd_2(H_2ppty)_2(SO_4)_2(H_2O)_2]·3H_2O(1)和[Cd_2(ppty)(SO_4)(H_2O)_2]_n(2)(H_2ppty=3,5-bis-(1H-pyrazol-3-yl)-[1,2,4]triazol-4-ylamine)。进一步的研究表明,1和2的结构分别包含有双核和四核镉簇单元,呈现出零维和二维的结构。并且在室温下对2个配合物的荧光性质也进行了测试。固体紫外漫反射表明1和2的光学带隙分别为1.87和2.32 e V,因此它们对亚甲基蓝的光降解反应表现出了良好的催化活性。展开更多
A metal-organic coordination polymer [ZnE.s（phen）（BDC）2（OH）]2 （phen = 1,10- phenanthroline, BDC = benzene-1,4-dicarboxylic acid） 1 has been hydrothermally synthesized and structurally characterized by single-c...A metal-organic coordination polymer [ZnE.s（phen）（BDC）2（OH）]2 （phen = 1,10- phenanthroline, BDC = benzene-1,4-dicarboxylic acid） 1 has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analyses and IR spectroscopy. The complex crystallizes in the triclinic system, space group PI with a = 11.199（2）, b = 11.593（2）, c = 11.865（3）/A, α= 99.330（1）, β = 111.506（1）, γ = 104.804（1）^o, V= 1328.4（5）A^3, Dc= 1.722 g/cm^3, Z = 1, Mr = 1377.82, F（000） = 692,μ（MoKa） = 2.306 mm^-1, S = 1.093, R= 0.0281 and wR = 0.0756 for 4179 observed reflections （I 〉 2σ（/））. The coordination polyhedron around Zn（II） can be described as a tetrahedron, trigonal bipyramid and octahedron. It is worth noting that the crystal structure of 1 is composed of tetranuclear zinc clusters linked by {ZnO6} units.展开更多
Through the reaction of Co 2(CO) 8 with four ligands containing P ?S? N atoms, cobalt carbonyl sulfur clusters Co 3(CO) 7( μ 3-S)〔 μ,η 2 -CNC(CH 3) 2P(S)(Cl)N(Ph)](Ⅰ)and Co 3 (CO) 7( μ 3-S)〔 μ,η 2 -SC(NH2)N-N...Through the reaction of Co 2(CO) 8 with four ligands containing P ?S? N atoms, cobalt carbonyl sulfur clusters Co 3(CO) 7( μ 3-S)〔 μ,η 2 -CNC(CH 3) 2P(S)(Cl)N(Ph)](Ⅰ)and Co 3 (CO) 7( μ 3-S)〔 μ,η 2 -SC(NH2)N-N=CH-C 6H 5〕 (Ⅱ),two tetranu-clear cobalt carbonyl clusters Co 4(CO) 10( μ 4 -S)( μ 4 -PC 6H 4OCH 3)(Ⅲ) and Co 4(CO) 10( μ 4-S)( μ 4-PC 6H 4OC 2H 5)(Ⅳ) ,were prepared and characterized by elementary analysis?IR? 1HNMR and MS spectroscopy.It was shown that bothⅠand Ⅱ have a tetrahedral framework Co 3S , both Ⅲ and Ⅳ have a octahedral framework Co 4SP. (Ⅰ)and Co 3 (CO) 7( μ 3-S)〔 μ,η 2 -SC(NH2)N-N=CH-C 6H 5〕 (Ⅱ),two tetranu-clear cobalt carbonyl clusters Co 4(CO) 10( μ 4 -S)( μ 4 -PC 6H 4OCH 3)(Ⅲ) and Co 4(CO) 10( μ 4-S)( μ 4-PC 6H 4OC 2H 5)(Ⅳ) ,were prepared and characterized by elementary analysis?IR? 1HNMR and MS spectroscopy.It was shown that bothⅠand Ⅱ have a tetrahedral framework Co 3S , both Ⅲ and Ⅳ have a octahedral framework Co 4SP.展开更多
基金supported by the NNSFC(No.20871023)the Jilin Provincial Science Research Foundation of China(No.20101549)+1 种基金Xiaonei Foundation of Changchun University of TechnologyThe 12th Five-Year Plan for Science&Technology Research sponsored by Department of Education of Jilin Province(Nos.130 and 146,2013)
文摘A unique metal-organic framework [Cd2（L）1.5（μ3-OH）（H2 O）2 ]·2H2 O（1, H2 L = 2,5-dibenzoylterephthalic acid） has been synthesized under hydrothermal conditions, and characterized by single-crystal X-ray diffractions, elemental analyses, IR spectra and fluorescence spectrum. The compound is of triclinic system, space group P1, C33 H27 CdO14, Mr = 870.33, a = 12.2939（17）, b = 12.5135（9）, c = 13.2046（10）, α = 115.3190（10）, β = 96.9140（10）, γ = 109.7950（10）°, V = 1641.6（3）3, Z = 2, Dc = 1.761 g/cm3, F（000） = 862, μ（MoK） = 1.366 mm-1, Rint = 0.0148, R = 0.0240 and wR = 0.0639 for 5995 observed reflections with I 〉 2σ（I）. X-ray analysis shows that the title complex exhibits a 3D framework with（412·63） topology, in which the tetra-nuclear [Cd4（μ3-OH）2 ] clusters act as 6-connected nodes, and the L ligands can be simplified to be linear connectors. Moreover, the thermal stability and fluorescence have been studied in detail.
基金financially supported by the National Natural Science Foundation of China(No.21161006)Program for Excellent Talents in Guangxi Higher Education Institutions(Gui Jiao Ren[2012]41)Program of the first session backbone teacher of Guangxi of China
文摘A new tetranuclear cluster [Co4（bm）6C12]＇（H20）2-（CH3OH） （1, Hbm is （1H-benzi- midazol-2-yl）-methanol） has been synthesized by solvothermal method and structurally determined by IR, elemental analysis, and single-crystal X-ray diffraction. Complex 1 belongs to monoclinie space group P21/n with a = 21.1713（5）, b = 12.7948（3）, c = 24.0195（9） А, β = 95.309（3）°, V = 6478.6（3） A3, Z = 4, F（000） = 2568, Dc = 1.289 g.cm-3, Mr = 1257.63,μ= 9.096 mm-I, S = 1.000, the final R = 0.0861 and wR = 0.2552 for 4956 observed reflections with 1 〉 20（/）. Two connected face-sharing cubes are observed in the framework of 1, each with one vertex missing. Complex 1 forms a 2-D network through N-H...O hydrogen bonds. The apparent holes can be observed.
文摘The cluster compound[Mo_4S_4(μ-O_2CC_5H_5)_2(dtp)_4](dtp=S_2P(OEt)_2)was obtained by the ligand substitution reaction of tetranuclear molybdenum cluster [Mo_4S_4(μ-dtp)_2(dtp)_4]in the mixed solvent of acetone,ethanol and water in the presence of C_6H_5CO_2Na.It is monoclinic and crystallizes in space group C2/c, Mr=1495.09,a=12.175(5),b=22.01(1),c=20.875(9),β=99.04(4)°;V=5575(5);Z=4; Dc=1.78g/cm^3.Final R factor is 0.066.The result reveals that the[Mo_4S_4]cluster core and t-(dtp)^(-1)ligands are retained and only μ-bridged(dtp)^(-1)ligands are substituted by(C_6H_5CO_2)^(-1)in the substitution reaction,thus producing the new title cluster compound,the structure of which contains two species of bidentate ligand.
基金Work supported by the National Natural Science Foundation of China(NNSFC)
文摘The new cluster[Mo_4(μ_3-O)_2O_4Cl_2(o-CH_3C_6H_4COO)_6]has been prepared by the reaction of molybdenum pentachloride and o-methylbenzoic acid.The crystal and molecular structures were determined by the X-ray diffraction method.It crystallizes in the orthorhombic space group Pnna with cell parameters:Mr=1361.6,a=13.792(4), b=17.957(3),c=20.974(9) ,V=5194(2) ~3,Z=4,Dc=1.74/cm^3,F(OOO)=2704,μ(MoK ) =11.0/cm,R=0.074.
基金Supported by the National Natural Science Foundation of China(Nos. 20476011 and 20371007).
文摘The self-assembly of clusters in inorganic systems is an interesting subject. The self-assembly of big molecules has been well established in biological systems. In addition, the coordination chemistry of metal-sulfur-nitrogen cluster complexes has been a very active and attracting field for many years as a result of the novelty and versatility of the crystal structures and reactivities of such clusters, as well as their potential applications as the models for the active sites in non-heme proteins. At the same time, there is currently considerable interest in the formation of metal complexes with heterocyclic ligands because of the diverse characteristics of ligands and their consequential wide range of applications.
基金supported by the Foundation of State Key Laboratory of Coal Conversion(No.J17-18-611)the National Natural Science Foundation of China(No.21676258)
文摘Two novel zinc（Ⅱ） coordination polymers, [Zn2（BCB）（CH3OH）（μ3-OH）]n（1） and {[Zn2（BCB）（μ3-OH）（H2O）2]·CH3OH}n （2）, have been constructed from 3,5-bis（2-carboxylphenoxy）benzoic acid（H3BCB） and characterized by elemental analysis（EA）, IR, powder X-ray diffraction（PXRD）, and thermogravimetric（TG） analyses. Structural analysis reveals that complexes 1 and 2 are both 1D polymeric chains with unprecedented tetranuclear {Zn4（COO）4（μ3-OH）2} clusters, which were further expanded into a 2D structure. Fluorescence measurements show that 1 and 2 have highly selective and sensitive detection of nitrobenzene.
基金supported by the National Natural Science Foundation of China(No.21771043,51572050 and 21601038)Guangxi Natural Science Foundation(No.2015GXNSFDA139007 and 2016GXNSFAA380085)Guangxi Key Laboratory of Electrochemical and Magnetochemical Functional Materials(EMFM20162107)
文摘2-(2,3-Dihydroxpropyliminomethyl)6-methoxyphenol(H3L), trimethylacetic acid(Hpiv), Gd(NO3)3·6 H2O and Co(NO3)2·6 H2O were reacted in Me OH to obtain a heterometallic tetranuclear cluster [Gd2Co2(L)2(μ3-OH)2(piv)6]·2 Hpiv·2 CH3OH(1). X-ray crystallographic analysis reveals that compound 1 was found to be a butterfly heterometallic tetranuclear cluster. The crystal(C64H108Co2Gd2N2O28, Mr = 1785.88) belongs to the triclinic crystal system, space group P1 with a =11.9798(6), b = 12.0877(5), c = 15.0367(7) A, α = 67.320(4)°, β = 81.583(4)°, γ = 75.201(4)°, V =1939.62(18) A3, Z = 1, T = 293.15 K, R = 0.048 and w R = 0.144 for 16299 observed reflections with I > 2σ(I). In magnetization study, heterometallic 1 exhibits magnetocaloric effect(MCE) of 14.75 J·kg-1·K-1 at 2 K for ΔH = 5 T, while it does not show non-linear response of the ac-susceptibilities.
基金supported by the National Natural Science Foundation of China(No.21473030)the Natural Science Foundation of Fujian Province(No.2013J01041)the Foundation of State Key Laboratory of Structural Chemistry(No.20130012)
文摘Two lanthanide-oxo-cluster polymers were synthesized by hydrothermal reaction using Ln_2O_3 as initial lanthanide materials：[Ln_4（SO_4）_4（OH）_4（H_2O）_7]·_4H_2O（Ln = Er 1,Ho 2）,and characterized by PXRD,IR spectra,X-ray single-crystal diffraction,2D IR correlation spectra and UV-visible absorption spectra.Single-crystal X-ray analyses reveal that compounds 1 and 2 are isostructural,and they are both crystallized in the orthorhombic system Pccn space group.Compound 1 is a 3D lanthanide cluster polymer based on tetranuclear cubane-like [Er_4（μ_3-OH）_4]^8＋ cations and SO_4^2- anions.The overall structure of 1 can be assigned to 6-connected pcu-type topology with the point symbol of（4^12.6^3）.
文摘通过改变溶剂热反应温度,合成了2个结构不同的镉配合物[Cd_2(H_2ppty)_2(SO_4)_2(H_2O)_2]·3H_2O(1)和[Cd_2(ppty)(SO_4)(H_2O)_2]_n(2)(H_2ppty=3,5-bis-(1H-pyrazol-3-yl)-[1,2,4]triazol-4-ylamine)。进一步的研究表明,1和2的结构分别包含有双核和四核镉簇单元,呈现出零维和二维的结构。并且在室温下对2个配合物的荧光性质也进行了测试。固体紫外漫反射表明1和2的光学带隙分别为1.87和2.32 e V,因此它们对亚甲基蓝的光降解反应表现出了良好的催化活性。
基金The project was supported by the Education Office of Jilin Province (No. 0047)
文摘A metal-organic coordination polymer [ZnE.s（phen）（BDC）2（OH）]2 （phen = 1,10- phenanthroline, BDC = benzene-1,4-dicarboxylic acid） 1 has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analyses and IR spectroscopy. The complex crystallizes in the triclinic system, space group PI with a = 11.199（2）, b = 11.593（2）, c = 11.865（3）/A, α= 99.330（1）, β = 111.506（1）, γ = 104.804（1）^o, V= 1328.4（5）A^3, Dc= 1.722 g/cm^3, Z = 1, Mr = 1377.82, F（000） = 692,μ（MoKa） = 2.306 mm^-1, S = 1.093, R= 0.0281 and wR = 0.0756 for 4179 observed reflections （I 〉 2σ（/））. The coordination polyhedron around Zn（II） can be described as a tetrahedron, trigonal bipyramid and octahedron. It is worth noting that the crystal structure of 1 is composed of tetranuclear zinc clusters linked by {ZnO6} units.
文摘Through the reaction of Co 2(CO) 8 with four ligands containing P ?S? N atoms, cobalt carbonyl sulfur clusters Co 3(CO) 7( μ 3-S)〔 μ,η 2 -CNC(CH 3) 2P(S)(Cl)N(Ph)](Ⅰ)and Co 3 (CO) 7( μ 3-S)〔 μ,η 2 -SC(NH2)N-N=CH-C 6H 5〕 (Ⅱ),two tetranu-clear cobalt carbonyl clusters Co 4(CO) 10( μ 4 -S)( μ 4 -PC 6H 4OCH 3)(Ⅲ) and Co 4(CO) 10( μ 4-S)( μ 4-PC 6H 4OC 2H 5)(Ⅳ) ,were prepared and characterized by elementary analysis?IR? 1HNMR and MS spectroscopy.It was shown that bothⅠand Ⅱ have a tetrahedral framework Co 3S , both Ⅲ and Ⅳ have a octahedral framework Co 4SP. (Ⅰ)and Co 3 (CO) 7( μ 3-S)〔 μ,η 2 -SC(NH2)N-N=CH-C 6H 5〕 (Ⅱ),two tetranu-clear cobalt carbonyl clusters Co 4(CO) 10( μ 4 -S)( μ 4 -PC 6H 4OCH 3)(Ⅲ) and Co 4(CO) 10( μ 4-S)( μ 4-PC 6H 4OC 2H 5)(Ⅳ) ,were prepared and characterized by elementary analysis?IR? 1HNMR and MS spectroscopy.It was shown that bothⅠand Ⅱ have a tetrahedral framework Co 3S , both Ⅲ and Ⅳ have a octahedral framework Co 4SP.
