We herein present the preparation, crystal structure, magnetic properties, and theoretical study of new heterobimetallic chains of formula {[Fe(III)(bpym)(CN4)]2M(II)(H2O)2}.6H2O [bpym = 2,2'-bipyrimidine; M = Zn (2), Co (3), Cu (4), and Mn (5)] which are obtained by using the building block PPh4[Fe(bpym)(CN)4].H2O (1) (PPh4+= tetraphenylphosphonium) as a ligand toward the fully solvated MII ions. The structure of complex 1 contains mononuclear [Fe(bpym)(CN)4]- anions. Compounds 2-5 are isostructural 4,2-ribbonlike bimetallic chains where the [Fe(bpym)(CN)4]- unit acts as a bis-monodenate ligand through two of its four cyanide ligands toward the M atom. Water hexamer clusters (4) and regular alternating fused six- and four-membered water rings with two dangling water molecules (2, 3, and 5) are trapped between the cyanide-bridged 4,2-ribbonlike chains. 1 and 2 behave as magnetically isolated low-spin iron(III) centers. 3 behaves as a single-chain magnet (SCM) with intrachain ferromagnetic coupling, slow magnetic relaxation, hysteresis effects, and frequency-dependent ac signals at T < 7 K). As expected for a thermally activated process, the nucleation field (Hn) in 3 increases with decreasing T and increasing v. Below 1.0 K, Hn becomes temperature independent but remains strongly sweep rate dependent. In this temperature range, the reversal of the magnetization may be induced by a quantum nucleation of a domain wall that then propagates due to the applied field. 4 and 5 are ferro- and ferrimagnetic chains respectively, with metamagnetic-like behavior (4). DFT-type calculations and QMC methodology provided a good understanding of the magnetic properties of 3-5.

Magnetic chain compounds have been actively investigated in the field of molecular magnetism for the design and synthesis of molecule-based magnets because of their possibility to achieve long-range magnetic order via interchain interactions. [1,2] Recent findings regarding magnetic hysteresis effects on one-dimensional (1D) compounds, [3] which are not associated with a three-dimensional (3D) magnetic order but with a slow magnetic relaxation, have provided an experimental confirmation of Glauberts' prediction [4] and opened exciting new perspectives of storing information in low-dimensional magnetic materials.The reported examples of these so-called molecular magnetic nanowires or single-chain magnets (SCMs) are: i) [Co-(hfacac) 2 (NITPhOMe)] (hfacac = hexafluoroacetylacetonate, NITPhOMe = 4¢-methoxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) which is a ferrimagnetic chain composed of high-spin cobalt(II) ions and nitronyl nitroxide radicals alternately arranged in a trigonal helix; [7]Here we report the X-ray structure [8] and magnetic proper-

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Two polymeric malonato-bridged copper(II) complexes of formulas [(H(2)bpe)[Cu(mal)2]]n.4nH2O (1) and [Cu(4")(mal)(4)(bpe)(3)]n.6nH(2)O (2) [mal = malonate dianion; bpe = 1,2-bis(4-pyridyl)ethylene] have been synthesized and characterized by X-ray diffraction. Complex 1 crystallizes in triclinic space group P(-)1, Z = 1, with unit cell parameters a = 4.8831(10) A, b = 9.585(2) A, c = 11.813(2) A, alpha = 77.29(3) degrees, beta = 82.18(3) degrees, and gamma = 84.92(3) degrees, whereas complex 2 crystallizes in the monoclinic space group P2(1)/n, Z = 4, with unit cell parameters a = 13.462(3) A, b = 10.275(5) A, c = 19.579(4) A, and beta = 105.21(3) degrees. The structure of 1 consists of anionic malonato-bridged uniform copper(II) chains which are connected through hydrogen bonds involving malonate-oxygen atoms, noncoordinated water molecules, and H(2)bpe(2+) cations. The intrachain copper-copper separation through carboxylate-malonate bridge in the anti-syn conformation is 4.8831(10) A. Complex 2 possesses a three-dimensional structure made up of neutral corrugated malonated-bridged copper(II) layers linked through bis-monodentate bpe molecules. The copper(II) atoms within each layer are bridged by a double mu-oxo and four carboxylato-malonate bridges with copper-copper separations of 3.4095(7) A (through oxo) and 4.9488(11)-6.5268(13) A (through carboxylato). The shortest interlayer copper-copper separation across bridging bpe is 13.434(3) A. Variable-temperature magnetic measurements (2-290 K) show an overall ferromagnetic behavior for both compounds. The magnetic pathway of complex 1 is through a single carboxylate-malonate bridge connecting apical and equatorial positions of adjacent copper(II) atoms, and the value of the magnetic coupling (J) for 1 through a numerical expression for a ferromagnetic uniform chain of interacting local doublets is J = +0.049(1) cm(-1). The values for the magnetic couplings through the main intralayer exchange pathways in 2 which correspond to carboxylate-malonate bridges connecting equatorial-equatorial (J(1)) and equatorial-apical (J(2)) coordination sites and to the double mu-oxo bridge linking equatorial-apical (J(5)) positions have been determined through a simplified model. The three magnetic couplings are weak, two of them being ferromagnetic (J(1) = +23(1) cm(-1) and J(2) = +6.5(1) cm(-1)) and the other one antiferromagnetic [zJ' = -1.0(1) cm(-1)]. The values of the magnetic couplings in 1 and 2 compare well with those previously reported for similar malonato-bridged copper(II) complexes of different dimensionalities.