Dual Channel H2O2 Photosynthesis in Pure Water over S-Scheme Heterojunction Cs3PMo12/CC Boosted by Proton and Electron Reservoirs.

Dual channel photo-driven H2O2 production in pure water on small-scale on-site setups is a promising strategy to provide low-concentrated H2O2 whenever needed. This process suffers, however, strongly from the fast recombination of photo-generated charge carriers and the sluggish oxidation process. Here, insoluble Keggin-type cesium phosphomolybdate Cs3PMo12O40 (abbreviated to Cs3PMo12) is introduced to carbonized cellulose (CC) to construct S-scheme heterojunction Cs3PMo12/CC. Dual channel H2O2 photosynthesis from both H2O oxidation and O2 reduction in pure water has been thus achieved with the production rate of 20.1 mmol L-1 gcat. -1 h-1, apparent quantum yield (AQY) of 2.1% and solar-to-chemical conversion (SCC) efficiency of 0.050%. H2O2 accumulative concentration reaches 4.9 mmol L-1. This high photocatalytic activity is guaranteed by unique features of Cs3PMo12/CC, namely, S-scheme heterojunction, electron reservoir, and proton reservoir. The former two enhance the separation of photo-generated charge carriers, while the latter speeds up the torpid oxidation process. In situ experiments reveal that H2O2 is formed via successive single-electron transfer in both channels. In real practice, exposing the reaction system under natural sunlight outdoors successfully results in 0.24 mmol L-1 H2O2. This work provides a key practical strategy for designing photocatalysts in modulating redox half-reactions in photosynthesis.

Facile and controllable preparation of carbon microsphere for electro-driven nitrogen reduction: Accommodating nitrogen doping with hierarchical porous structure.

Driven by sustainable electricity, electrochemical nitrogen fixation under ambient conditions is considered as a promising strategy to generate low-concentrated NH3/NH4+. Under the principle of doping and porous engineering, nitrogen-doped carbon microsphere with hierarchical pores (NC-HP) is fabricated via pyrolyzing polymer microsphere. Hierarchical structure with macro-, meso- and micropores is obtained by assembling melamine/phenol-formaldehyde oligomers in Pickering droplets, with the assistance of triblock copolymer Pluronic F127. The regularity of mesopores is strongly affected by melamine to phenol mass ratio. For NC-HP, nitrogen content (N-content) in the carbon matrix can reach as high as 19.1 wt%, yet trade-off effect is observed between N-content and regularity of mesopores. As consequence, NC-HP-3 with N-content of 15.6 wt% and distinct mesopores exhibits the highest catalytic performance. At -0.5 V vs. RHE, NH3/NH4+ production rate and Faradaic efficiency (FE) value reach 15.6 µg∙mgcat.-1∙h-1 and 15.5%, respectively. It shows excellent recyclability, and no degradations are observed with respect to morphology and porous structure. In this hierarchical porous structure, mesopores are expected to facilitate mass transfer for both electrolyte ions and nitrogen, and hence catalytic active sites (e.g. pyrrolic- and pyridinic-N species) in hierarchically mutually connected pores can be well utilized.

Methyl nitrate energetic compounds based on bicyclic scaffolds of furazan-isofurazan (isoxazole): syntheses, crystal structures and detonation performances.

Two energetic bicyclic scaffolds (furazan-isoxazole and furazan-1,3,4-oxadiazole) were constructed via different cyclization reactions. Based on the energetic bicyclic scaffolds, the energetic compounds, 3-(4-nitraminofurazan-3-ly)-isoxazole-5-methylnitrate 1c and 5-(4-nitraminofurazan-3-ly)-1,3,4-oxadiazole-2-methylnitrate 2c, were designed and synthesized in good yields. Because of the acidity of nitramine, the corresponding energetic ionic salts, ammonium 3-(4-nitraminofurazan-3-ly)isoxazole-5-methylnitrate 1d and ammonium 5-(4-nitraminofurazan-3-ly)-1,3,4-oxadiazole-2-methylnitrate 2e, were also obtained and well characterized, their structures were further determined by X-ray single crystal diffraction. To have a better understanding of the structure-property relationships of furazan-bicyclic scaffolds and nitrate groups, their thermal behaviors, detonation performances and the sensitivities were investigated via differential scanning calorimetry (DSC), ESP analysis, Hirshfeld surfaces calculation, EXPLO5 program and BAM standard techniques. Compared with those of ammonium 5-(4-nitraminofurazan-3-ly)-1,2,4-oxadiazole-2-methylnitrate 3e, the results show that all these methyl nitrate energetic compounds based on bicyclic scaffolds of furazan-isofurazan exhibit good detonation performances and extraordinary insensitivities. As supported by experimental and theoretical data, the formation of energetic ionic salts causes an increase of the weak interactions, significantly improving the thermal performance over 110 °C.

Regulating Electronic Structure in Bi2 O3 Architectures by Ti Mediation: A Strategy for Dual Active Sites Synergistically Promoting Photocatalytic Nitrogen Hydrogenation.

Under mild conditions, nitrogen undergoes the associative pathways to be reduced with solar energy as the driving force for fixation, avoiding the high energy consumption when undergoing dissociation. Nevertheless, this process is hindered by the high hydrogenation energy barrier. Herein, Ti was introduced as hard acid into the δ-Bi2 O3 (Ti-Bi2 O3 ) lattice to tune its local electronic structure and optimize its photo-electrochemistry performance (reduced bandgap, increased conduction band maximum, and extended carrier lifetime). Heterokaryotic Ti-Bi dual-active sites in Ti-Bi2 O3 created a novel adsorption geometry of O-N2 interaction proved by density functional theory calculation and N2 temperature-programmed desorption. The synergistic effect of dual-active sites reduced the energy barrier of hydrogenation from 2.65 (Bi2 O3 ) to 2.13 eV (Ti-Bi2 O3 ), thanks to the highly overlapping orbitals with N2 . Results showed that 10 % Ti-doped Bi2 O3 exhibited an excellent ammonia production rate of 508.6 µmol gcat -1 h-1 in water and without sacrificial agent, which is 4.4 times higher than that of Bi2 O3 . In this work, bridging oxygen activation and synergistic hydrogenation for nitrogen with Ti-Bi dual active sites may unveil a corner of the hidden nitrogen reduction reaction mechanism and serves as a distinctive strategy for the design of nitrogen fixation photocatalysts.

A PW12/Ag functionalized mesoporous silica-coated magnetic Fe3O4 core-shell composite as an efficient and recyclable photocatalyst.

The novel composite, Fe3O4@SiO2@mSiO2-PW12/Ag, was successfully prepared by in situ loading Ag nanoparticles (Ag NPs) on the surface of grafted phosphotungstate (denoted as PW12) Fe3O4@SiO2@mSiO2via a photoreduction deposition method. PW12 not only acts as a reducing agent and stabilizer for Ag NPs but also as a bridge to link Ag NPs and the SiO2 shell in the loading process. Its activity toward the photodegradation of methyl orange (MO) and photoreduction of Cr2O72- anions was evaluated. Experimental results showed that Fe3O4@SiO2@mSiO2-PW12/Ag with 5.3 wt% Ag loading and 18.65 wt% of PW12 exhibits the highest photocatalytic efficacy, and complete degradation of MO and 91.2% photoreduction of Cr(vi) were realized under simulated sunlight for 75 min, respectively. The enhanced catalytic activities of the composite are due to its high specific surface area, the synergistic effect among the components and the formation of a heterojunction of PW12/Ag. The possible enhanced photocatalytic mechanism is proposed. The catalyst is durable and can be easily recovered using a magnet for recycling without a significant loss of catalytic activity.

Structural investigation of one- and three-dimensional lanthanide(III) coordination polymers based on functionalized terpyridine carboxylate and aromatic dicarboxylate ligands.

Three series of lanthanide coordination polymers, namely catena-poly[[lanthanide(III)-µ2-(benzene-1,2-dicarboxylato)-µ2-[2-(2,2':6',2''-terpyridin-4'-yl)benzoato]] monohydrate], {[Ln(C8H4O4)(C22H14N3O2)]·H2O}n or {[Ln(1,2-bdc)(L)]·H2O}n, with lanthanide (Ln) = dysprosium (Dy, 1), holmium (Ho, 2) and erbium (Er, 3), poly[bis(µ2-benzene-1,3-dicarboxylato)bis[µ2-2-(2,2':6',2''-terpyridin-4'-yl)benzoato]dilanthanide(III)], [Ln2(C8H4O4)2(C22H14N3O2)2]n or [Ln2(1,3-bdc)2(L)2]n, with Ln = gadolinium (Gd, 4), Ho (5) and Er (6), and poly[(µ2-benzene-1,4-dicarboxylato)[µ2-2-(2,2':6',2''-terpyridin-4'-yl)benzoato]lanthanide(III)], [Ln(C8H4O4)(C22H14N3O2)]n or [Ln(1,4-bdc)(L)]n, with Ln = Dy (7), Ho (8), Er (9) and ytterbium (Yb, 10), were synthesized under hydrothermal conditions and characterized by elemental analysis, IR and single-crystal X-ray diffraction. Compounds 1-3 possess one-dimensional loop chains with Ln2(COO)2 units, which are extended into three-dimensional (3D) supramolecular structures by π-π interactions. Isostructural compounds 5 and 6 show 6-connected 3D networks, with pcu topology consisting of Ln2(COO)2 units. Compounds 7-10 display 8-connected 3D frameworks with the topological type rob, consisting of Ln2(COO)2 units. The influence of the coordination orientations of the aromatic dicarboxylate groups on the crystal structures is discussed.

Dy(iii) zig-zag chains assembled in a 3D framework with single-molecule magnet behaviour.

A new lanthanide-based framework, [Dy(STP)(1,2-bdc)]n (1), was constructed. It represents dysprosium(iii) 1D zigzag chains in a 3D framework and displays single-molecule magnet (SMM) behaviour with an energy barrier of 55.76 K under zero dc field.

A large, X-shaped polyoxometalate [As6Fe7Mo22O98]25- assembled from [AsMo7O27]9- and [FeMo4O19]11- moieties.

A large X-shaped polyoxometalate, [As6Fe7Mo22O98]25- (1), has been synthesized and structurally characterized. The skeleton of 1 is composed of two monocapped hexavacant Keggin [AsMo7O27]9- units and two divacant Anderson [FeMo4O19]11- units fused together through a central Fe5O4 core and two µ4-As2O bridging units, resulting in a unique tetramer with C2h symmetry. The polyanion represents the largest iron-containing arsenomolybdate to date and it contains an unprecedented heptanuclear iron(iii) cluster. The investigation of the magnetic properties shows that the Fe7 cluster exhibits an overall ferromagnetic interaction with a spin ground state of S = 7.5.

Lanthanide coordination frameworks constructed from 3,3',4,4'-diphenylsulfonetetracarboxylic and 1,10-phenanthroline: synthesis, crystal structures and luminescence properties.

Two series of lanthanide coordination polymers, [Ln(Hdpstc)(H2O)2]n·nH2O (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Er (7), Yb (8)) and [Ln(Hdpstc)(phen)(H2O)]n·1.5nH2O (Ln = Pr (9), Nd (10), Eu (11), Tb (12)) (H4dpstc = 3,3',4,4'-diphenylsulfonetetracarboxylic acid and phen = 1,10-phenanthroline), have been hydrothermally synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction. Isostructural compounds 1-8 and 9-12 exhibit (3,6)-connected 2D layered structures with Hdpstc3- anions as bridges. The Eu3+ and Tb3+ compounds exhibit bright red and green emissions with absolute quantum yields of 11.19% for 2-Eu, 26.05% for 4-Tb, 35.74% for 11-Eu, and 48.05% for 12-Tb. With a rational design strategy, we have constructed a series of Tb3+-doped Eu3+ materials emitting tunable three primary colors towards efficient white light emission with compounds 2-Eu and 4-Tb, and the absolute quantum yield of white light emission is 13.58%. Meanwhile, 4-Tb displays a highly sensitive response toward Fe3+ ions through significant fluorescence quenching of Tb3+.

Synthesis, Structure, White-Light Emission, and Temperature Recognition Properties of Eu/Tb Mixed Coordination Polymers.

Two series of Eu(III)/Tb(III) coordination polymers, [LnL(glu)]n·2nH2O (Ln = Eu (1), Tb (2)) and [LnL(glu)(H2O)]n (Ln = Eu (3), Tb (4)) [HL = (2-(2-sulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline, H2glu = glutaric acid] have been hydrothermally synthesized by controlling the pH values and characterized by elemental analysis, infrared spectra, and single-crystal X-ray diffraction. Isomorphic compounds 1 and 2 exhibit 6-connected 3D network with the pcu topological net, containing left- and right-handed helical chains. Isomorphic compounds 3 and 4 show 3,4-connected 2D new topology with the point symbol of (4(2)·6(3)·8)(4(2)·6). Multicolor luminescence can be tailored from red to green regions by singly varying the mixing molar ratio of Eu(III)/Tb(III) cations. The mixing component of 1Eu/2Tb = 4:6 not only achieves white-light emission with the CIE coordinate of (0.323, 0.339) upon excitation at 405 nm but also presents a temperature recognition property with the significantly high sensitivity of 0.68% per K in the 50-225 K temperature range upon excitation at 370 nm.

Incorporation of M(H2O)6(2+) between layers {M(H2O)2Ru2(CO3)4Cl2}n(2n-) (M = Zn, Mn): syntheses, structures and magnetic properties.

Isostructural heterometallic diruthenium carbonates KM(H2O)6[M(H2O)2Ru2(CO3)4Cl2]·4H2O [M = Zn (1) and Mn (2)] were synthesized from the reaction of the precursors [Ru2(CO3)4Cl2](5-) and transitional metal ions in aqueous solution. Complexes 1 and 2 show layered structures in which Ru2(II,III) units are linked by four octahedral environment M(H2O)2(2+) ions in a cross fashion and vice versa giving a negative bimetallic square grid layer {M(H2O)2Ru2(CO3)4Cl2}n(3n-). M(H2O)6(2+) ions, linked by K(+) forming zigzag chain {KM(H2O)6}n(3+), are located in the void spaces between the layers. The adjacent bimetallic carbonate layers are connected with K-O and K-Cl bonds, and hydrogen bonding, forming a supramolecular 3D framework structure. Their magnetic properties were characterized in detail, and intralayer ferromagnetic coupling between the Ru2 dimer and Mn(2+) ion, as well as long-range ordering (Tc = 5.2 K) coexistence of domain movement behavior were observed for complex 2.

Cadmium diruthenium(II,III) carbonates showing diverse magnetism behavior arising from variety configuration of [Ru2(CO3)4]n(3n-) layer.

Two hetero-metallic carbonates, namely KCd(H2O)3Ru2(CO3)4·4H2O (1) and KCd(H2O)3Ru2(CO3)4·3.5H2O (2), have been synthesized in a neutral aqueous solution. Both of the 3D dimensional structured complexes contain mixed-valent diruthenium(II,III) carbonate paddlewheel cores of Ru2(II,III)(CO3)4(3-) that are connected to each other in trans- or cis-modes by carbonate oxygen atoms, forming rectangular square-grid and isomeric parallelogram layers [Ru2(CO3)4]n(3n-) in 1 and 2, respectively. The reaction temperature is found to play an important role in directing the final products with particular topologies and their layered structural diversity is due to the various linking modes between the Ru2(CO3)4(3-) units. The magnetic studies show that ferromagnetic interactions are propagated between the diruthenium units in both complexes 1 and 2 but their magnetic properties differ at low temperatures, in which the trans linking mode parallelogram layer [Ru2(CO3)4]n(3n-) in complex 2 leads to long-range magnetic ordering below 4.0 K. However, no Curie ordering down to 1.8 K is detected for complex 1 containing the isomeric rectangle square-grid layer linking in the cis mode.

Single-molecule magnet based on a C-type polyoxomolybdate with an S = 11 ground state: [Fe5CoMo22As2O85(H2O)]15-.

A C-type polyoxomolybdate containing a mixed-transition metal cluster Fe(5)Co has been prepared as an ammonium salt, (NH(4))(15)[Fe(5)CoMo(22)As(2)O(85)(H(2)O)]·15H(2)O (1). Interestingly, the magnetism measurements show that the compound exhibits not only an overall ferromagnetic cluster with a large spin ground state of S = 11 but also the behavior of single-molecule magnets.

An unusual fan-type polyanion with a silver cation located at the axial center, [AgAsIII2(AsIIIAsVMo4O18(OH)2)3]11-.

A new type of polyoxomolybdate containing mixed-valence arsenic, [AgAs(III)(2)(As(III)As(V)Mo(4)O(18)(OH)(2))(3)](11-) (1), has been synthesized. Single-crystal X-ray analysis was carried out on (NH(4))(5)(C(2)H(9)N(2))(4.5)H(1.5)[AgAs(III)(2)(As(III)As(V)Mo(4)O(18)(OH)(2))(3)]·14H(2)O (1a) and (NH(4))(11)[AgAs(III)(2)(As(III)As(V)Mo(4)O(18)(OH)(2))(3)]·16H(2)O (1b). The polyanion is composed of three unprecedented [As(III)As(V)Mo(4)O(18)(OH)(2)](6-) subunits linked together by two AsO(3) trigonal-pyramidal structures from both sides via sharing six bridging oxygen atoms, and a silver cation is enclosed in the center of the polyanion and coordinated by three As atoms with the As-Ag-As bond angle of 120°, to lead to a fan-like structure with an approximative C(3h) symmetry. The polyanion was also characterized by IR, X-ray photoelectron spectroscopy and thermogravimetry-differential scanning calorimetry. The stability of [AgAs(III)(2)(As(III)As(V)Mo(4)O(18)(OH)(2))(3)](11-) in an aqueous solution was investigated by electronic absorbance spectroscopy and electrospray ionization mass spectrometry, and the possible disaggregation mechanism of the polyanion is proposed.

A diruthenium soft ferromagnet showing T(c) = 3.0 K: Mn4(H2O)16H[Ru2(CO3)4]2[Ru2(CO3)4(H2O)2]·11H2O.

A three-dimensional CO(3)(2-)-bridged Mn(II)-Ru(2)(II,III) complex, Mn(4)(H(2)O)(16)H[Ru(2)(CO(3))(4)](2)[Ru(2)(CO(3))(4)(H(2)O)(2)]·11H(2)O (1), was synthesized by self-assembling Ru(2)(CO(3))(4)(3-) paddle-wheel precursors and Mn(2+) cations. It contains an unprecedented layer [Ru(2)(CO(3))(4)](n)(3n-) with (4,4) network. The ferromagnetic coupling between spin centers results in ordering below 3.0 K.

Double sandwich polyoxometalate and its Fe(III) substituted derivative, [As2Fe5Mo21O82]17­ and [As2Fe6Mo20O80(H2O)2]16­.

A double sandwich polyoxometalate and its Fe(III) substituted derivative, [As(2)Fe(5)Mo(21)O(82)](17-) (1) and [As(2)Fe(6)Mo(20)O(80)(H(2)O)(2)](16-) (2), were synthesized and characterized by single-crystal X-ray diffraction, infrared spectroscopy, fluorescent spectroscopy, UV spectra, thermogravimetry-differential scanning calorimetry analyses, electrospray ionization mass spectrometry, and magnetism measurements. The polyoxoanion is composed of a central fragment FeMo(7)O(28) for 1 (Fe(2)Mo(6)O(26)(H(2)O)(2) for 2) and two external AsMo(7)O(27) fragments linked together by two distinct edge-sharing dimeric clusters Fe(2)O(10) to lead to a C(2v) molecular symmetry. The central FeMo(7)O(28) fragment and external AsMo(7)O(27) fragment have a similar structure, and both of them can be viewed as a monocapped hexavacant α-Keggin subunit with a central FeO(4) group or a central AsO(3) group. Both of the polyoxoanions contain a oxo-bridged Fe(III)(5) magnetic core with the angles of Fe-O-Fe in the range of 96.4(4)-125.7(5)°, and magnetism measurements show an overall ferromagnetic interactions among the five-nuclearity cluster Fe(5) with the spin ground state S = 15/2.

Combined DFT and BS study on the exchange coupling of dinuclear sandwich-type POM: comparison of different functionals and reliability of structure modeling.

The exchange coupling of a group of three dinuclear sandwich-type polyoxomolybdates [MM'(AsMo7O27)2](12-) with MM' = CrCr, FeFe, FeCr are theoretically predicted from combined DFT and broken-symmetry (BS) approach. Eight different XC functionals are utilized to calculate the exchange-coupling constant J from both the full crystalline structures and model structures of smaller size. The comparison between theoretical values and accurate experimental results supports the applicability of DFT-BS method in this new type of sandwich-type dinuclear polyoxomolybdates. However, a careful choice of functionals is necessary to achieve the desired accuracy. The encouraging results obtained from calculations on model structures highlight the great potential of application of structure modeling in theoretical study of POM. Structural modeling may not only reduce the computational cost of large POM species but also be able to take into account the external field effect arising from solvent molecules in solution or counterions in crystal.

Three banana-shaped arsenomolybdates encapsulating a hexanuclear transition-metal central magnetic cluster: [As(III)2Fe(III)5MMo22O85(H2O)]n- (M = Fe3+, n = 14; M = Ni2+ and Mn2+, n = 15).

Three polyoxometalates encapsulating high-nuclearity magnetic clusters MFe(5), [As(2)MFe(5)Mo(22)O(85)(H(2)O)](n-) (M = Fe(3+), n = 14; M = Ni(2+) and Mn(2+), n = 15), were synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis, and magnetism measurements. The polyanion [As(2)MFe(5)Mo(22)O(85)(H(2)O)](n-) consists of a central MMo(7)O(28) (M = Fe(3+), Ni(2+), and Mn(2+)) fragment and two AsMo(7)O(27) fragments linked together by two trimeric clusters, Fe(2)MoO(µ(2)-O)(2) and Fe(3)(H(2)O), to form a banana-shaped structure with C(1) symmetry. The MMo(7)O(28) and AsMo(7)O(27) units have a similar structure and can be considered as a monocapped hexavacant α-B-Keggin subunit with a central MO(4) group or a central As(III)O(3) group. The polyoxometalates have a low absorption of υ(Mo-O(d)) (925-913 cm(-1)) because most of the Mo atoms in the polyanions have at least two longer Mo-O(d) bonds. The framework of the arsenomolybdates is stable before As(2)O(3) escaping (ca. 300 °C). The analysis of magnetostructural correlations and magnetism measurements indicate the coexistence of ferro- and antiferromagnetic interactions, which give an overall ferromagnetic spin ground state in the compounds.

A cagelike polyanion with a Ag+ enwrapped, [AgAs2Mo15O54]11-.

The polyanion [AgAs(2)Mo(15)O(54)](11-) has an unusual cage-like structure composed of [AsMo(6)O(27)](15-) and [AsMo(6)O(24)](9-) subunits connected by three MoO(4) tetrahedra, and a Ag(+) cation is inclosed at the center of the cage and coordinated by two As atoms with a As-Ag-As bond angle of 180° along with three µ(3)-oxo groups from MoO(4) tetrahedra to lead to a trigonal-pyramidal coordination geometry. The compound was also characterized by IR, X-ray photoelectron spectroscopy, fluorescent spectroscopy, and thermogravimetry-differential scanning calorimetry. The stability of [AgAs(2)Mo(15)O(54)](11-) in aqueous solution was investigated by using electronic absorbance spectroscopy and electrospray ionization mass spectrometry.

AsMo7O27-bridged dinuclear sandwich-type heteropolymolybdates of Cr(III) and Fe(III): magnetism of [MM'(AsMo7O27)2]12- with MM' = FeFe, CrFe, and CrCr.

Two new dinuclear sandwich-type heteropolymolybdates based on the mulitidendate inorganic fragment [AsMo(7)O(27)] and Cr(III) and Fe(III) ions, namely, the homometallic sandwich polyoxometalate (POM) (NH(4))(12)[Fe(2)(AsMo(7)O(27))(2)] x 12 H(2)O (1) and the first example of the "symmetrical" heterometallic Cr(III)-Fe(III) sandwich POM, (NH(4))(12)[FeCr(AsMo(7)O(27))(2)] x 13 H(2)O (2), were simultaneously synthesized in high yield. Their magnetic properties are thoroughly investigated together with the homometallic sandwich POM (NH(4))(12)[Cr(2)(AsMo(7)O(27))(2)] x 11 H(2)O (3). The chi(M)T values for compounds 1-3 at 300 K correspond well to the calculated spin-only values for Fe(III) (S = 5/2) and Cr(III) (S = 3/2) with g(Fe) = g(Cr) = 2. Upon cooling, the chi(M)T values decline monotonously and reach 0.14, 1.00, and 0.11 cm(3) K mol(-1) at 2.0 K for 1, 2, and 3, respectively, indicating a significant antiferromagnetic exchange between the magnetic centers with J = -2.09, -4.09, and -6.26 cm(-1), respectively, for 1, 2, and 3. The magnetic results clearly establish that compound 2 is formed by bimetallic Cr(III)-Fe(III) units and not by a mixture of the two antiferromagnetically coupled homometallic species. Their thermal properties are also characterized.