A tetradentate bisoxime and its supramolecular nickel(II) cluster: synthesis,crystal structure,and spectral properties

Salen-type bisoxime 5,5′-dimethoxy-2,2′-[(ethylenedioxy)bis(nitrilomethylidyne)]diphenol (H₂L) and its trinuclear Ni(II) cluster {[(NiL)(n-BuOH)]₂(μ-OAc)₂Ni}?·?n-BuOH have been synthesized and structurally characterized. The structure of H₂L adopts an L-shape conformation where the two salicylaldoxime moieties are well separated. In the trinuclear Ni(II) cluster, two acetates coordinate to three Ni(II)'s through Ni–O–C–O–Ni bridges, four μ-phenoxos from two [NiL(n-BuOH)] units also coordinate to Ni(II), and two n-butanols coordinate to two terminal Ni(II)'s forming a distorted octahedral geometry. The Ni–O–C–O–Ni and μ-phenoxo bridges play important roles in assembling Ni(II) and the ligands. H₂L forms a rectangle-like large cave structure through O–H?···?N, C–H?···?O, and C–H?···?π hydrogen-bond interactions, whereas its trinuclear Ni(II) cluster exhibits a 3-D supramolecular network structure through intermolecular O–H?···?O, C–H?···?O, and C–H?···?π hydrogen-bond interactions.     

Syntheses,crystal structures,and magnetic properties of two new manganese(II) complexes based on biphenyl-2,5,2′,5′-tetracarboxylic acid

Two new complexes, [Mn(H₂bptc)(2,2′-bpy)₂]?·?2H₂O (1) and [Mn₃(Hbptc)₂(2,2′-bpy)₃(H₂O)₈]?·?2H₂O (2) (H₄bptc?=?biphenyl-2,5,2′,5′-tetracarboxylic acid, 2,2′-bpy?=?2,2′-bipyridine), have been synthesized under hydrothermal conditions. Their structures have been characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, powder X-ray diffraction, and thermogravimetric analyses. Complexes 1 and 2 are both linked into 3-D supramolecular networks by non-covalent interactions (O–H?···?O, C–H?···?O, C–H?···?π, and π?···?π). Complexes 1 and 2 exhibit weak antiferromagnetic interactions.     

Three double- or triple-stranded chains constructed from different cobalt(II) salts and a flexible bis-triazole ligand

Three coordination compounds, {[Co(btrp)₂(H₂O)₂]?·?NO₃?·?H₂O} _n (1), {[Co(btrp)₂(H₂O)₂]?·?H₂O?·?2H₂btc} _n (2), and {[Co(btrp)₃]?·?2ClO₄} _n (3) (btrp?=?1,3-bis(1,2,4-triazol-1-yl)propane; H₃btc?=?benzene-1,3,5-tricarboxylic acid), have been prepared via solvothermal method and characterized by single-crystal X-ray diffraction and elemental analyses. Compound 1 possesses a 1-D double-stranded chain composed of ribbons of 20-membered cycles. Binuclear water clusters link adjacent nitrate anions to form a 1-D supramolecular helix in the structure. Compound 2 has a 1-D double-stranded chain wherein free H₂btc ligands constitute 1-D negative chains through classical hydrogen-bonding interactions (O–H?···?O). Compound 3 exhibits a triple-stranded 1-D chain. For 1–3, 3-D supramolecular structures are consolidated by interchain weak hydrogen-bonding interactions as well as electrostatic interactions.     

Three Cu(II) (R)-2-chloromandelato complexes generated from dipyridyl-type ligands with different spacer lengths: syntheses,crystal structures,and ferroelectric properties

Three Cu(II) complexes, Cu₂(bpy)(H₂O)(Clma)₂ (1), Cu₂(bpe)(H₂O)₂(Clma)₂ (2), and Cu(bpp)(Clma) (3), were synthesized (HClma = (R)-2-Chloromandelic acid, bpy?=?4,4′-dipyridine, bpe?=?1,2-di(4-pyridyl)ethylene, bpp?=?1,3-di(4-pyridyl)propane). Complexes 1, 2, and 3 are constructed from 1-D coordination arrays generated from Cu₂(H₂O)(Clma)₂, Cu₂(H₂O)₂(Clma)₂, and Cu₂(Clma)₂ moieties and linked through bpy, bpe, and bpp co-ligands, respectively. 1 and 2 are assembled into 3-D supramolecular networks via O–H?O hydrogen bonds with topology of (6³)(6⁹·8) and (4¹²·6³), respectively, and 3 is assembled into a 3-D architecture through C–H?O hydrogen bonds with topology of (4³·6³)(4³)(4⁴·6⁵·8)(4⁶·6⁶·8³). Compounds 1, 2, and 3 crystallized in acentric space groups P2₁, P1, and P2₁, which exhibit significant ferroelectricity (remnant polarization Pr?=?0.008?μC?cm^?2, coercive field Ec?=?21.4?kV?cm^?1, the spontaneous saturation polarization Ps?=?0.167?μC?cm^?2 for 1, Pr?=?0.183?μC?cm^?2, Ec?=?1.69?kV?cm^?1, and Ps?=?0.021 μC?cm^?2 for 3). Results from infrared and thermal analyses are also discussed.     

Synthesis,structures and characterization of two new supramolecular coordination complexes with the ambidentate ligand 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot)

Two new coordination supramolecular complexes based on a versatile and unsymmetrical 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and Mn^II and Ni^II have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of MnCl₂?· 4H₂O with Hpot afforded a neutral mononuclear complex [Mn(pot)₂(H₂O)₄]?·?2H₂O (1), which exhibits a three-dimensional (3-D) supramolecule through versatile intermolecular O–H?···?X (X=O, N and S) hydrogen bond interactions. When using NiCl₂?·?6H₂O instead of MnCl₂?· 4H₂O under similar reaction conditions, a neutral mononuclear complex [Ni(pot)₂(H₂O)₄] (2) is also obtained, which does not exhibit intermolecular hydrogen bonds and π–π stacking interactions. It is very interesting that the pot anion exhibits different coordination modes in complexes 1 and 2. The IR spectra and the TGA for 1 and 2 have been investigated and discussed in detail.     

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.     

Two cadmium(II) addition compounds with 3-hydroxy-2,7-naphthalenedisulfonate containing aromatic diamines and their 3-D net

{[CdCl(2,2′-bipy)₂(H₂O)]⁺·[Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?·3H₂O} (1) and {[Cd(phen)₃]²⁺·2[Cd(3-O^?-2,7-NDS)(phen)₂]^?·8.5H₂O} (2) (3-OH-2,7-NDS?=?3-hydroxy-2,7-naphthalenedisulfonate, phen?=?1,10-phenanthroline, and 2,2′-bipy?=?2,2′-bipydine) were prepared and characterized by X-ray single-crystal diffraction. Compound 1 contains a discrete coordination cation [CdCl(2,2′-bipy)₂(H₂O)]⁺ and a coordination anion [Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?; 2 contains a discrete coordination cation [Cd(phen)₃]²⁺ and two coordination anions [Cd(3-O^?-2,7-NDS)(phen)₂]^?. There are numerous weak interactions among the coordination cation, coordination anion, and free water molecules, such as O–H?···?O hydrogen bonds, π?···?π stacking, and Cl^??···?π interactions in 1 and π?···?π stacking and C–H?···?π interactions in 2. The cations and anions as building blocks are connected to construct different 3-D supramolecular architectures via weak intermolecular interactions. Particularly, the capsule structure of 1 was observed.     

Unusual coordination features and self-assembly of a crown ether complex [Na2(2,3-naphtho-15-crown-5)2(NO3)][Cu(NO3)3(H2O)]

A novel supramolecular complex, [Na₂(2,3-naphtho-15-crown-5)₂(NO₃)][Cu(NO₃)₃(H₂O)] (1), has been prepared and characterized by X-ray single crystal diffraction. The complex crystallizes in the triclinic system, space group Pī, with a?=?11.233(6), b?=?13.342(7), c?=?16.601(8)?Å, α?=?89.836(7), β?=?79.132(8), γ?=?66.545(7)°, V?=?2234(2)?ų, Z?=?2 and final R ₁(wR ₂)?=?0.0467(0.1164). Novel coordination features and supramolecular architectures are found in the solid state of 1. Two [Na(2,3-naphtho-15-crown-5)]⁺ cations containing two different sodium coordination numbers (six and seven) are bridged by a tridentate nitrate group, to form a larger complex cation, [Na₂(2,3-naphtho-15-crown-5)₂(NO₃)], which is assembled into a novel 1D zigzag chain-like structure through aromatic C–H?···?π interactions.     

Supramolecular architecture built of Co(II) and a tripodal ligand containing 1-D water tapes with (H2O)16 cluster units

The reaction of Co(NO₃)₂?·?6H₂O with a tripodal ligand leads to a new complex {[Co(L)]?·?2NO₃?·?8H₂O} (1) confirmed by single-crystal X-ray diffraction, infrared spectroscopy, and elemental analysis. The particular interest of 1 is in the formation of a 1-D water tape consisting of (H₂O)₁₆ cluster units, the neighboring water tapes are connected by free nitrate anions via hydrogen bonds into a 2-D guest layer. These guest layers are alternately packed face-to-face with the 2-D host layers along the a-axis to form a 3-D supramolecular architecture. There exist C–H?···?N and C–H?···?O weak hydrogen bonds between the guest layer and host layer. These weak hydrogen bonds and water–nitrate, water–water hydrogen bonds are important for the stability of the overall structure.     

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.     

Syntheses and structures of three chiral complexes derived from nucleophilic addition of L-proline to di-2-pyridyl ketone

In the presence of nickel acetate, a chiral ligand, (S)-Hdphp ((S)-N-[di(2-pyridyl)-hydroxy-methyl]-proline), was synthesized in situ by nucleophilic addition of L-proline to di-2-pyridyl ketone. Based on this ligand, three chiral mononuclear complexes, {Ni[(S)-dphp](DMF)(H₂O)}(ClO₄) (1), {Ni[(S)-dphp](H₂O)₂}(ClO₄)(H₂O)_1.5 (2), and {Ni[(S)-dphp](SCN)(H₂O)} (3), have been obtained and characterized by single-crystal X-ray diffraction, elemental analyses, and infrared spectra. By virtue of charge-assisted O–H?···?O hydrogen-bonding interactions, all the complexes possess double chain structures. The double chains were connected into 2-D networks via π?···?π stacking and CH?···?π interactions in 1. For 2, O–H?···?O hydrogen-bonding interactions between free water molecules and other oxygens as well as π?···?π stacking and CH?···?π interactions extend the chains into a 3-D network. Complex 3 exhibits 3-D structure via O–H?···?S interactions.     

Crystal structures and luminescence of two cadmium(II) polymers constructed from aromatic polycarboxylate and bis(1,2,4-triazol-1-yl)methane ligands

Two new coordination compounds, {[Cd₂(btrm)(ip)₂(H₂O)₂]?·?2H₂O} _n (1) and {[Cd₂(btrm)(hip)₂(H₂O)₄]?·?3H₂O} _n (2) (btrm?=?bis(1,2,4-triazol-1-yl)methane, H₂ip?=?isophthalic acid, H₂hip?=?5-hydroxy isophthalic acid), have been synthesized and structurally characterized. Compound 1 is a 3-D network with CdSO₄ topology. Compound 2 contains 1-D ladder structures, which are interconnected by classical hydrogen-bonding interactions (O–H?···?O) to lead to 3-D supramolecular architectures. Luminescence was performed on 1 and 2, both of which showed strong fluorescent emissions in the solid state at room temperature.     

Supramolecular interactions in high molecular weight bisdithiocarbamate adducts of divalent Zn(II), Cd(II), and Hg(II): spectral,VBS, and single crystal X-ray structural studies on MS4N2 chromophores

This article describes supramolecular interactions induced in a high molecular weight dithiocarbamate, padtc, by its design. Synthesis, spectral studies involving zinc, cadmium and mercury, padtc, and adducts with tmed, such as [Zn(padtc)₂] (1), [Zn(padtc)₂(tmed)]?·?C₆H₅CH_3?·?0.5(H₂O) (2), [Cd(padtc)₂] (3), [Cd(padtc)₂(tmed)]?·?C₆H₅CH₃?·?0.36(H₂O) (4), [Hg(padtc)₂]?·?H₂O (5), [Hg(padtc)₂(2,2′-bipy)]?·?H₂O (6), [Hg(padtc)₂(1,10-phen)]?·?H₂O (7), and [Hg(padtc)₂(oxine)]?·?H₂O (8) (where padtc^??=?N,N′-(iminodiethylene)bisphthalimidedithiocarbamate, 1,10-phen?=?1,10-phenanthroline, tmed?=?tetramethylethylenediamine, 2,2′-bipy?=?2,2′-bipyridine, oxine?=?8-hydroxyquinoline) along with the single crystal X-ray structural analysis of [Zn(padtc)₂(tmed)]?·?C₆H₅CH₃?·?0.5(H₂O) (2) and [Cd(padtc)₂(tmed)]?·?C₆H₅CH₃?·?0.36(H₂O) (4) are reported. All the complexes were characterized by IR, NMR (¹H and ¹³C), and thermogravimetric study. The IR spectra of the complexes show the contribution of the thioureide form to the structures. In ¹³C NMR spectra, the most important thioureide (N¹³CS₂) carbon signals are observed at 210–212?ppm. Single crystal X-ray structural analyses of 2 and 4 show the presence of extensive supramolecular interactions stabilizing the solid-state structure. Both zinc and cadmium are in a distorted octahedral environment with MS₄N₂ chromophores. VBS of Zn and Cd are 1.76 and 1.98, respectively, supporting the correctness of the determined structure and the valence of the central metal ions.     

Three new coordination frameworks based on 2-ethyl-imidazole-4,5-dicarboxylate and 1,10-phenanthroline: syntheses,crystal structures,and luminescence

Three new coordination polymers based on 2-ethyl-imidazole-4,5-dicarboxylate with 1,10-phenanthroline as ligands, Pb(HEIDC)(phen)₂ (1), [Zn(EIDC)(phen)] _n (2), and {[Ba(H₂EIDC)₂(phen)]?·?(phen)₂?·?[Ba(H₂EIDC)(HEIDC)(phen)]} _n (3) (H₃EIDC?=?2-ethyl-1-Himidazole-4,5-dicarboxylate; phen?=?1,10-phenanthroline), have been synthesized under hydrothermal conditions and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Complex 1 displays a tetranuclear square constructed of four Pb(II) centers, four HEIDC, and eight phen, resulting in a 3-D network with a 1-D open channel along the c-axis via C–H?···?O hydrogen bonds, C–H?···?π, and π–π stacking interactions. Complex 2 is an infinite zigzag chain resulting in the final 3-D supramolecular framework via C–H?···?O and π–π stacking interactions. Complex 3 is composed of two individual Ba chains, exhibiting a 3-D framework via O–H?···?O, O–H?···?N hydrogen bonds, and π–π stacking interactions. The photoluminescence spectra of 1 and 2 in the solid state have been investigated, 1 exhibits green photoluminescence in the solid state at room temperature.     

Co(en)3[B4O5(OH)4]Cl·3H2O和[Ni(en)3][B5O6(OH)4]2·2H2O的合成、结构以及热力学性质

利用水热法合成了两种过渡金属配合物为模板剂的含水硼酸盐晶体Co(en)3[B4O5(OH)4]Cl·3H2O(1) 和 [Ni(en)3][B5O6(OH)4]2·2H2O (2),并通过元素分析、X射线单晶衍射、红外光谱及热重分析对其进行了表征。化合物1晶体结构的主要特点是在所有组成Co(en)33+, [B4O5(OH)4]2–, Cl– 和 H2O之间通过O–H…O、O–H…Cl、N–H…Cl和N–H…O四种氢键连接形成网状超分子结构。化合物2晶体结构的特点是[B5O6(OH)4]–阴离子通过O–H…O氢键连接形成沿a方向有较大通道的三维超分子骨架,模板剂[Ni(en)3]2+阳离子和结晶水分子填充在通道中。     

Synthesis,Crystal Structure and Magnetic Behaviour of {[Co(dimb)2(H2O)2]·(NO3)2·(H2O)2}n

The title complex {[Co(dimb)₂(H₂O)₂]·(NO₃)₂·(H₂O)₂}_n ( 1 ) (dimb = 1,3‐di(imidazol‐1‐ylmethyl)‐5‐methylbenzene) has been hydrothermally synthesized by the reaction of dimb with Co(NO₃)₂·6H₂O in aqueous solution. The cobalt(II) atoms are linked by bridging dimb ligands to form 2D corrugated and wavy networks containing Co₄(dimb)₄ macrocyclic motifs. Two neighboring independent layers interlinked each other in a parallel fashion to construct three‐dimensional structure by O–H···O, N–H···O and C–H···O hydrogen bonds. Magnetic measurement shows the weak antiferromagnetic interaction with a one‐dimensional chain model in the range of 5–300 K, with J of –0.68 cm⁻¹.     

Two solvent directed zinc(II) coordination polymers with 1-D single-zigzag chain and 1-D double-zigzag chains

Two coordination polymers, {[Zn(NiL)(DMA)(H₂O)₂] (DMA)(H₂O)} _n (1) (DMA?=?N,N-dimethylacetamide) and {[Zn₂(NiL)₂(DMF)(H₂O)₄]?·?3DMF} _n (2) (DMF?=?N,N-dimethylformamide), have been prepared by reactions of Zn(NO₃)₂?·?6H₂O and NiL in CH₂Cl₂-DMA–H₂O and CH₂Cl₂-DMF–H₂O, respectively. H₂L denotes dimethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo-9,10-benzo-[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate. Single-crystal X-ray diffraction analyses reveal that coordination geometries around Ni(II) are identical with slightly distorted square planar and all Ni–N bonds are very short. Complex 1 shows 1-D zigzag chain structure, while 2 has 1-D double-zigzag chains. The chains, which are packed parallel in 1 and 2, are interconnected by lattice solvent through O–H···O and C–H···O hydrogen bonds to form 3-D supramolecular networks. We discuss solvent effects on assembly of the two coordination polymers. The results reveal that coordinated solvent has influence on the assembly procedure.     

Complexes of Co(II), Ni(II), and Cu(II) with 4-(3,4-dichlorophenyl)-1,2,4-triazole

Novel oligonuclear complexes of Co(II), Ni(II), and Cu(II) with 4-(3,4-dichlorophenyl)-1,2,4-triazole (L) of the composition [M₃L₁₀(H₂O)₂](NO₃)₆ (M = Co(II), Ni(II)), [Ni₃L₆(H₂O)₆]Hal₆ (Hal = Cl^?, Br^?), and [Cu₅L₁₆(H₂O)₂](NO₃)₁₀ · 2H₂O were synthesized and studied by magnetic susceptibility, electronic and IR spectroscopy, and powder X-ray diffraction methods. All the above complexes are X-ray amorphous. Antifer-romagnetic exchange interactions between the M²⁺ ions were discovered in the [Co₃L₁₀(H₂O)₂](NO₃)₆ and [Ni₃L₁₀(H₂O)₂](NO₃)₆ complexes, whereas ferromagnetic exchange interactions were observed in the complexes [Ni₃L₆(H₂O)₆]Cl₆, [Ni₃L₆(H₂O)₆]Br₆, and [Cu₅L₁₆(H₂O)₂](NO₃)₁₀ · 2H₂O.     

Three 1-D molybdenum(V) phosphates with copper/nickel coordination cations

Three 1-D reduced molybdenum(V) phosphates, [Ni(OH)₂][Na₂(H₂O)₃]₂{Ni[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?5H₂O (1), [Ni(H₂O)₂][K(H₂O)₅]₂{Ni[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?4H₂O (2), and [Cu(H₂O)₂][Na(H₂O)₅]₂{Cu[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?4H₂O (3), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The crystallographic analysis reveals that 1 is based on {Ni[Mo₆O₁₂(OH)₃(HPO₄)₃(PO₄)]₂} clusters connected through {[Ni(OH)₂][Na₂(H₂O)₃]₂} pentanuclear mixed-metal cluster units to yield unusual 1-D chains along the c-axis, which further form 3-D supramolecular networks via hydrogen-bonding. Compounds 2 and 3 are heterogeneous isostructural compounds. Both are built from M[Mo₆P₄]₂ (M?=?Ni or Cu) blocks as the structural motif combined with [MO₄(H₂O)₂] (M?=?Ni or Cu) octahedra to form 1-D chains, where M[Mo₆P₄]₂ (M?=?Ni or Cu) is bonded by [M′(H₂O)₅] (M′?=?K or Na). Furthermore, bulk carbon paste electrode modified with 1 (1-CPE) displays good electrocatalytic activity toward reduction of nitrite or bromate.     

The standard molar enthalpy of formation of Ce2(MoO4)3(s) and Sm2(MoO4)3(s) using solution calorimetry

The enthalpies of formations of Ce₂(MoO₄)₃(s) and Sm₂(MoO₄)₃(s) have been measured at 298.15 K using semi adiabatic solution calorimetry. The precipitation reaction between RE(NO₃)₃·6H₂O(s) (R= Ce, Sm) and ammonical solution of Na₂MoO₄(s) was studied. From the enthalpy of precipitation and other required auxiliary data, $ \Updelta_{\text{f}} H_{\text{m}}^{ \circ } \left( { 2 9 8. 1 5 {\text{ K}}} \right) $ Δ f H m ° ( 2 9 8.1 5 K ) of Ce₂(MoO₄)₃(s) and Sm₂(MoO₄)₃(s) have been calculated for the first time as ?4388.7 ± 3.6 and ?4363.4 ± 4.1 kJ mol^?1, respectively. The enthalpy of hydration of anhydrous Ce(NO₃)₃(s) to Ce(NO₃)₃·6H₂O(s) has been calculated. $ \Updelta_{\text{f}} H_{\text{m}}^{ \circ } \left( {{\text{MoO4}}^{ 2- } ,\,{\text{aq}},\, 2 9 8. 1 5 \,{\text{K}}} \right) $ Δ f H m ° ( MoO4 2 ? , aq , 2 9 8.1 5 K ) has also been measured and calculated as ?995.1 kJ mol^?1 from required literature data.