Juan Modesto Clemente-Juan

University of Valencia | UV · Instituto de Ciencia Molecular (ICMol)

The effects of the vibronic coupling in quantum cellular automata (QCA) based on the square planar mixed valence (MV) molecular cells comprising four paramagnetic centers (spin cores) and two excess mobile electrons are analyzed in the important particular case when the Coulomb energy gap between the ground antipodal diagonal‐type two‐electron conf...

The effect of the double exchange in a square-planar mixed-valence dn+1−dn+1−dn−dn–type tetramers comprising two excess electrons delocalized over four spin cores is discussed. The detailed analysis of a relatively simple d2−d2−d1−d1–type tetramer shows that in system with the delocalized electronic pair the double exchange is able to produce antif...

We present a FORTRAN code based on a new powerful and efficient computational approach to solve multidimensional dynamic Jahn-Teller and pseudo Jahn-Teller problems. This symmetry-assisted approach constituting a theoretical core of the program is based on the full exploration of the point symmetry of the electronic and vibrational states. We also...

A synthetic procedure is presented to construct new magnetic polyoxometalates (POMs) containing one or two subunits of ‘[CoIIICo3II(OH)3(H2O)6−m(PW9O34)]3−' (m = 3 or 5). The substitution of the water ligands present in these subunits by oxo or hydroxo ligands belonging to other POM fragments, gives rise to four, larger POM anions: [Co7(OH)6(H2O)6(...

Combining Co(II) with the 2,6-bis-(pyrazol1-yl)pyridine ligand functionalized with a carboxylic acid group (bppCOOH) results in the compound [CoII(bppCOOH)2](ClO4)2·2Me2CO, which shows a field-induced slow relaxation of magnetization as a result of the magnetic anisotropy of the distorted octahedral coordination of high-spin Co(II). Co(II)/Fe(II) s...

The article summarizes the main results of application of the theory of the Jahn-Teller (JT) and pseudo JT effects to the description of molecular quantum dot cellular automata (QCA), a new paradigm of quantum computing. The following issues are discussed: 1) QCA as a new paradigm of quantum computing, principles and advantages; 2) molecular implem...

Polyoxometalate (POM) chemistry has recently offered excellent examples of single ion magnets (SIMs) and molecular spin qubits. Compared with conventional coordination compounds, POMs provide rigid and highly symmetric coordination sites. However, all POM-based SIMs reported to date exhibit a very limited range of possibilities for chemical process...

Low-temperature magnetometry, ac susceptibility, and calorimetry have been employed to study Co-based single-chain magnets (SCMs) organized through halogen bonding. Magnetic hysteresis and maxima in the dc and ac susceptibilities, respectively, confirm the SCM behavior of the system. Several characteristic magnetic relaxation regimes are observed a...

SIMPRE is a fortran77 code which uses an effective electrostatic model of point charges to predict the magnetic behavior of rare-earth-based mononuclear complexes. In this article, we present SIMPRE1.2, which now takes into account two further phenomena. First, SIMPRE now considers the hyperfine and quadrupolar interactions within the rare-earth io...

Four novel cobalt-substituted polyoxometalates having cobalt cores exhibiting cubane or dicubane topologies have been synthesized and characterized by IR, elemental analysis, electrochemistry, UV-vis spectroscopy, X-ray single-crystal analysis, and magnetic studies. The tetracobalt(II)-substituted polyoxometalate [Co4(OH)3(H2O)6(PW9O34)](4-) (1) co...

A new photoresponsive molecular polyanion in which two Fe(iii) ions are simultaneously coordinated by two [A-α-PW9O34]⁹⁻ polyoxometalate units and two oxalato ligands has been obtained. When irradiated with UV light its potassium salt, 1, exhibits a remarkable photocoloration effect, attributable to the partial reduction of the POM units to give ri...

Our interest in this article is prompted by the vibronic problem of charge polarized states in the four-dot molecular quantum cellular automata (mQCA), a paradigm for nanoelectronics, in which binary information is encoded in charge configuration of the mQCA cell. Here, we report the evaluation of the electronic levels and adiabatic potentials of m...

The family of cubic polyoxopalladates encapsulating lanthanide ions [LnPd12(AsPh)8O32]5- where Ln = Tb, Dy, Ho, Er and Tm, is magnetically characterised and theoretically described by the Radial Effective Charge (REC) model and a phenomenological crystal-field approach using the full-hamiltonian, in the SIMPRE and CONDON packages respectively. The...

We demonstrate that the borderline class II/III magnetic mixed valence (MV) dimers which can be referred to as single molecule multiferroics provide a unique possibility to achieve electric field control of the electron transfer (ET) dynamics. As an example we consider a MV dimer d2-d1 in which extra electron is delocalized over two spin-cores ( s0...

Herein we evaluate the influence of an electric field on the coupling of two delocalized electrons in the mixed-valence polyoxometalate (POM) [GeV14 O40 ](8-) (in short V14 ) by using both a t-J model Hamiltonian and DFT calculations. In absence of an electric field the compound is paramagnetic, because the two electrons are localized on different...

Simple electrostatic models have been shown to successfully rationalize the magnetic properties of mononuclear single molecule magnets based on f-elements and even to predict the direction of the magnetic anisotropy axis in these nanomagnets. In this Article, we go a step forward by showing that these models, conveniently modified to account for th...

This paper belongs to a series of contributions aiming at establishing a general library that helps in the description of the crystal field (CF) effect of any ligand on the splitting of the J ground states of mononuclear f-element complexes. Here, the effective parameters associated with the oxo ligands (effective charges and metal-ligand distances...

This is the installation and used manual of SIMPRE 1.1, a fortran77 code that can implement different effective electrostatic models based on point charges around a rare earth ion. The program calculates the full set of crystal field parameters, Stark energy levels and spin wave functions, as well as magnetic properties. The package has already bee...

We propose the use of an electric field stimulus to strongly affect the optical properties of ferromagnetic mixed-valence (MV) dimers. This proposal is based on the prediction of an anomalous Stark effect in the intervalence absorption bands of these multi-electron MV systems. As distinguished from the conventional Stark effect observed in one-elec...

The ferromagnetic tetranuclear nickel(II) complex [Ni-4(L)(4)(CH3OH)(2)]center dot 2MeOH center dot 8H(2)O (1) has been synthesized by reacting nickel nitrate hexahydrate with the Schiff base ligand H2L (H2L = N-(2-hydroxyphenyl)3-methoxy-salicylideneamine). Complex 1 was characterized by analytical, thermogravimetric, optical and magnetic techniqu...

Here we report the evaluation of the electronic and vibronic levels of mixed-valence tetra-ruthenium (2Ru(II) + 2Ru(III)) systems (assembled as two coupled Creutz-Taube complexes) for which possible molecular implementations of quantum-dot cellular automata was proposed. These complexes are representatives of Robin and Day classes I, II, and III an...

Quantum algorithms often assume independent spin qubits to produce trivial $|\uparrow\rangle=|0\rangle$, $|\downarrow\rangle=|1\rangle$ mappings. This can be unrealistic in many solid-state implementations with sizeable magnetic interactions. Here we show that the ground energy level structure of a molecule containing three exchange-coupled $^{159}...

Three novel octanuclear, hexanuclear and tetranuclear complexes of high-spin Fe(III) ions were obtained by the reaction of the N,N′-bis-(1R-imidazol-4-ylmethylene)-ethane-1,2-diamine ligand (R = H, CH3) and its derivatives with Fe(ClO4)3·6H2O and KSCN. The tetradentate Schiff-base ligand acts as a bis(bidentate) chelating bridge between two adjacen...

Three new heterometallic copper(II)-cobalt(II) complexes [(CuL(2))2Co{dca}2]·H2O(1), [(CuL(1))2Co{dca}2]n (2a), and [(CuL(1))2Co{dca}2]n (2b) [dca(-) = dicyanamide = N(CN)2(-)] have been synthesized by reacting the "metallo-ligand" [CuL(1)] or [CuL(2)] with cobalt(II) perchlorate and sodium dicyanamide in methanol-water medium (where H2L(1) = N,N'-...

A Radial Effective Charge model based on a point charge approach is applied in order to study the magnetic behavior of two lanthanoid single ion magnets coordinated by pyrazole-based ligands that produce a D3h crystal field. We obtain the lowest-lying magnetic levels and the associated wave functions of Dy(H2BPzMe22)3 (1), and the tricapped NdTp3 (...

Two cobalt phosphonates, [Co2 (2,2'-bpy)2 (H2 O)(pbtcH)] (1) and [Co2 (H2 O)(pbtcH)(phen)2 ] (2; pbtcH5 =5-phosphonatophenyl-1,2,4-tricarboxylic acid, 2,2'-bpy=2,2'-bipyridine, phen=1,10-phenanthroline), with layer structures are reported. Compound 1 contains O-C-O and O-P-O bridged tetramers of Co4 , which are further connected by pbtcH(4-) units...

The two-electron reduced mixed-valence polyoxometalate [GeV14O40](8-) presents an unusual paramagnetic behaviour as a consequence of the partial trapping of these electrons. The effect of applying an electric field is that of inducing antiferromagnetic coupling between the two delocalized electronic spins.

Polyoxometalate single ion magnet [GdW30P5O110](14-) () has been studied by generalized Rabi oscillation experiments. It was possible to increase the number of coherent rotations tenfold through matching the Rabi frequency with the frequency of the proton. Achieving high coherence with polyoxometalate chemistry, we show its excellent potential not...

This work presents a fortran77 code based on an effective electrostatic model of point charges around a rare earth ion. The program calculates the full set of crystal field parameters, energy levels spectrum, and wave functions, as well as the magnetic properties such as the magnetization, the temperature dependence of the magnetic susceptibility,...

We propose a microscopic analytical approach to the description of the low-temperature dissipative intracluster electron transfer dynamics in centrosymmetric one-electron mixed-valence (MV) dimers. The dissipative system (bath) is supposed to consist of the acoustic phonons of the crystal surrounding that are coupled to the delocalized electron(s)...

Herein, we describe the combination of polyoxometalates (POMs) with a polynuclear metallic cluster Mn4 {Mn4 = [Mn4(OAc)2(pdmH)6]2+, (pdmH = deprotonated pyridine-2,6-dimethanol; C7H8NO2)} for the construction of ionic crystals with layered architectures. Choosing a POM with the appropriate charge and size not only allows for the fine tuning of the...

Here we discuss the electronic and vibronic problems of mixed valency (MV) in molecular clusters which are of current interest in areas as diverse as solid-state chemistry, biochemistry, and molecular magnetism. Modern research in these areas is focused on the nanosized clusters at the border between classical and quantum scales and for this reason...

The novel polymeric chain copper(II) complex [Cu4(μ-Mesalpn)2(μ1,1,1-N3)2(μ1,1-N3)2Cu]n (1) was prepared by the reaction of Cu(NO3)2·3H2O with Mesalpn in the presence of an excess of NaN3. A single-crystal X-ray diffraction study showed an unusual 1D polymeric chain based on pentanuclear Cu5 units with both μ1,1,1-N3 and μ1,1-N3 bridges, and with t...

We analyze the magnetic behavior of the five uranium-based SIMs reported in the literature. By combining a corrected crystal field model with the magnetic experimental data, we obtain the lowest-lying magnetic levels and the associated wave functions of the nanomagnets, which are found to be compatible with the observed SMM behavior. Additionally,...

A series of homoleptic ([Tb(III) (Pc)(2) ]) and heteroleptic ([Tb(III) (Pc)(Pc')]) Tb(III) bis(phthalocyaninate) complexes that contain different peripheral substitution patterns (i.e., tert-butyl or tert-butylphenoxy groups) have been synthesized in their neutral radical forms and then reduced into their corresponding anionic forms as stable tetra...

Here we develop a general approach to calculating the energy spectrum and the wave functions of the low-lying magnetic levels of a lanthanoid ion submitted to the crystal field created by the surrounding ligands. This model allows us to propose general criteria for the rational design of new mononuclear lanthanoid complexes behaving as single-molec...

Herein, we present two geometrical models based on an effective point-charge approach to provide a full description of the lowest sublevels in lanthanoid single ion magnets (SIMs). The first one, named as the Radial Effective Charge (REC) model, evaluates the crystal field effect of spherical ligands, e.g. F(-), Cl(-) or Br(-), by placing the effec...

In this review we discuss the relevance of polyoxometalate (POM) chemistry to provide model objects in molecular magnetism. We present several potential applications in nanomagnetism, in particular, in molecular spintronics and quantum computing.

A robust, stable and processable family of mononuclear lanthanoid complexes based on polyoxometalates (POMs) that exhibit single-molecule magnetic behavior is described here. Preyssler polyanions of general formula [LnP(5)W(30)O(110)](12-) (Ln(3+) = Tb, Dy, Ho, Er, Tm, and Yb) have been characterized with static and dynamic magnetic measurements an...

Multiferroic molecules for spintronics: In a many-electron mixed-valence dimer with dominant double exchange, as compared with antiferromagnetic superexchange, the electric field is shown to induce a spin crossover from the ferromagnetic spin state to the antiferromagnetic one. This leads to a sharp decrease in the magnetic moment of the molecule a...

We show here that mixed-valence (MV) magnetic molecules with a significant electron delocalization are extremely sensitive to an external electric field. In particular, we focus on the symmetric many-electron MV binuclear complexes that are on the borderline between Robin and Day classes II and III. In these molecules, the double-exchange, which ha...

In this contribution, we predict and theoretically investigate the effects of the electric field pulse in mixed valence (MV) dimers. These systems exhibit bistability with a large internal dipole moment mediated by the itinerant electron trapped by the vibronic coupling. In this sense, they are similar to single molecular magnets (SMMs) that are bi...

We present a detailed experimental and theoretical study of a 1D spin .5ex1 -.1em/ -.15em.25ex2 Co-based molecular chain, trans-[CoCl2(3,5-Br2py)2]. Our results show distinct features that are associated to both intra-molecular interactions (along the chain) and inter-molecular interactions (perpendicular to the direction of chains). The hysteresis...

Two new trinuclear copper(II) complexes, [Cu(3)(μ(3)-OH)(daat)(Hdat)(2)(ClO(4))(2)(H(2)O)(3)](ClO(4))(2)·2H(2)O (1) and [Cu(3)(μ(3)-OH)(aaat)(3)(H(2)O)(3)](ClO(4))(2)·3H(2)O (2) (daat = 3,5-diacetylamino-1,2,4-triazolate, Hdat = 3,5-diamino-1,2,4-triazole, and aaat = 3-acetylamino-5-amino-1,2,4-triazolate), have been prepared from 1,2,4-triazole de...

We report ac susceptibility and continuous wave and pulsed EPR experiments performed on GdW10 and GdW30 polyoxometalate clusters, in which a Gd3+ ion is coordinated to different polyoxometalate moieties. Despite the isotropic character of gadolinium as a free ion, these molecules show slow magnetic relaxation at very low temperatures, characteristi...

A robust, stable and processable family of mononuclear lanthanoid complexes based on polyoxometalates (POMs) that exhibit single-molecule magnetic behavior is described here. Preyssler polyanions of general formula [LnP5W30O110]12– (Ln3+ = Tb, Dy, Ho, Er, Tm, and Yb) have been characterized with static and dynamic magnetic measurements and heat cap...

We theoretically investigate the effects of a magnetic pulse on a single-molecule magnet (SMM) initially magnetized by a dc field along the easy axis of magnetization. In the Landau–Zener (LZ) scheme, it is shown that the final spin state is a function of the shape and duration of the pulse, conditioned by the decoherence time of the SMM. In the ca...

Three high-nuclearity Ni-substituted polyoxotungstates (POTs)--[Ni(enMe)2(H2O)2]2[Ni(H2O)6]2[Ni(enMe)2][Ni(H2O)2]1.5[HNi20X4W34(OH)4O136(H2O)6(enMe)8]·11 H2O (3), [Ni(en)2(H2O)]2[H8Ni21X4W34(OH)4O136(en)10(H2O)5]·22 H2O (4), and [Ni(enMe)2]2[H6Ni22X4W34(OH)4O136(H2O)6(enMe)10]·18 H2O (5), in which en = ethylenediamine, enMe = 1,2-diaminopropane, X...

The secret is in the net: A 3D mixed ligated cobalt phosphonate [Co 3(pna)2(L)(H2O)2] (1) (pnaH 3=6-phosphonic nicotinic acid, L=1,4-bis(imidazol-1-ylmethyl)benzene) contains isolated ferromagnetic chains with interchain magnetic interactions. It experiences long-range magnetic ordering at approximately 3.4 K, below which magnetization relaxation a...

We present a low-temperature study of one-dimensional Co-based molecular chains, trans-[CoCl2(3,5-Br2py)2]. Ac and dc susceptibility experiments show that the cobalt ions tend to form anisotropic ferromagnetic chains, whose properties are dictated by the thermal excitations of 1D domain walls. The observation of anomalies in the hysteresis loops of...

In this critical review we review the problem of exchange interactions in polynuclear metal complexes involving orbitally degenerate metal ions. The key feature of these systems is that, in general, they carry an unquenched orbital angular momentum that manifests itself in all their magnetic properties. Thus, interest in degenerate systems involves...

In this paper we report the temperature and pH dependent syntheses and systematic characterization of four new Co(II)/Co(III) and Ni(II) complexes with a pentadentate Schiff base ligand H(3)L obtained by condensing 1,3,-diaminopropan-2-ol with 2-hydroxyacetophenone in 1:2 molar ratio. The room temperature syntheses involving Co(II) and Ni(II) nitra...

Molecular clusters are formed by a finite number of exchange-coupled paramagnetic centers and they are model systems between molecules and extended solids. In order to simulate their properties and extrapolate to solids, the size of the systems to be treated should be as large as possible. In this context, the use of efficient parallel codes is ess...

Four tetrameric nickel(II) pseudohalide complexes have been synthesized and structurally, spectroscopically, and magnetically characterized. Compounds 1-3 are isostructural and exhibit the general formula [Ni(2)(dpk·OH)(dpk·CH(3)O)(L)(H(2)O)](2)A(2)·2H(2)O, where dpk = di-2-pyridylketone; L = N(3)(-), and A = ClO(4)(-) for 1, L = NCO(-) and A = ClO...

This review article is a first attempt to give a systematic and comprehensive description (in the framework of the unified theoretical approach) of the exchange interactions in polynuclear systems based on orbitally degenerate metal ions in the context of their relevance to the modern molecular magnetism. Interest in these systems is related to the...

By slightly changing the synthetic conditions, we have prepared two closely related linear tetranuclear CuII complexes with the symmetrical ONNO donor tetradentate Schiff-base ligand [H2L=(OH)C6H4(CH3)CN(CH2)3NC(CH3)C6H4(OH)] and with azide ions. These two distinctly coloured crystalline products were characterized by elemental analysis, IR and UV–...

To explain the single-molecule magnet behavior of the mononuclear complex [(tpaMes)Fe](-) we have developed a model that takes into account the trigonal ligand field splitting of the atomic (5)D term of the Fe(II) ion, and the spin-orbital splitting and mixing of the ligand field terms. The ground ligand field term is shown to be the orbital double...

Four new Cu(II)-azido complexes of formula [CuL(N(3))] (1), [CuL(N(3))](2) (2), [Cu(7)L(2)(N(3))(12)](n) (3), and [Cu(2)L(dmen)(N(3))(3)](n) (4) (dmen = N,N-dimethylethylenediamine) have been synthesized using the same tridentate Schiff base ligand HL (2-[1-(2-dimethylaminoethylimino)ethyl]phenol, the condensation product of dmen and 2-hydroxyaceto...

Two linear cobalt chloride ferromagnetic chains, trans-[CoCl2(3,5-X2py)2] [X¼ Cl (1), Br (2)], have been prepared and the influence of the halogen bonding on the interchain magnetic interactions has been investigated.

Four novel heterometallic complexes [Co2Cr2(NCS)4(HDea)2(Dea)2]·4dmf (1), [Co2Cr2(NCS)4(HDea)2(Dea)2]·4dmso (2), [Mn2Cr2(NCS)4(HDea)2(Dea)2(dmf)2]·2dmf (3) and [Mn2Cr2(NCS)4(HDea)2(Dea)2(dmso)2]·4dmso (4) have been prepared using zerovalent cobalt (1, 2) or manganese (3, 4), Reineckes salt, ammonium thiocyanate and a non-aqueous solution of diethan...

We present a FORTRAN code based on a new powerful and efficient computational approach to solve the double exchange problem for high-nuclearity MV clusters containing arbitrary number of localized spins and itinerant electrons. We also report some examples in order to show the possibilities of the program.

We investigate the mechanism of spin-lattice relaxation of Er ions encapsulated in polyoxometalate clusters, which below 4 K can only reverse its spin via quantum tunneling processes. The temperature-independent rate tau-1 is, at zero field, ten orders of magnitude larger than the rates predicted for direct phonon-induced processes. In addition, we...

The aim of the work is to give an explanation of the magnetic properties of a mixed-valence [GeV14O40]8– polyoxometalate reduced by two electrons, which, in contrast to what happens in other two-electron-reduced polyoxometalates, does not show any magnetic coupling between the two unpaired electrons. For this purpose, a quantitative evaluation of t...

The greatest number of nickel ions incorporated into polyoxometalates to date are reported by G.-Y. Yang et al. in their Communication on page 7176 ff. The two largest nickel-substituted poly(polyoxotungstate)s are prepared by degradation reactions and structural directing effects of trilacunary Keggin {B-α-PW9O34} fragments under hydrothermal cond...

The preparation, magnetic characterization, and X-ray structures of two polycationic Mn(12) single-molecule magnets [Mn(12)O(12)(bet)(16)(EtOH)(4)](PF(6))(14).4CH(3)CN.H(2)O (1) and [Mn(12)O(12)(bet)(16)(EtOH)(3)(H(2)O)](PF(6))(13)(OH).6CH(3)CN.EtOH.H(2)O (2) (bet = betaine = (CH(3))(3)N(+)-CH(2)-CO(2)(-)) are reported. 1 crystallizes in the centro...

The sandwich-type tungstogermanates [Cu(3)(H(2)O)(B-beta-GeW(9)O(33)(OH))(B-beta-GeW(8)O(30)(OH))](12-) (1), [Co(H(2)O)(2){Co(3)(B-beta-GeW(9)O(33)(OH))(B-beta-GeW(8)O(30)(OH))}(2)](22-) (2), and [Mn(H(2)O)(2){Mn(3)(H(2)O)(B-beta-GeW(9)O(33)(OH))(B-beta-GeW(8)O(30)(OH))}(2)](22-) (3) were synthesized and characterized by single-crystal X-ray diffra...

Cited By (since 1996): 3, Export Date: 15 June 2012, Source: Scopus, CODEN: ICHAA, doi: 10.1016/j.ica.2008.10.003, Language of Original Document: English, Correspondence Address: Kokozay, V.N.; Department of Inorganic Chemistry, National Taras Shevchenko University, Volodymyrska Street 64, Kyiv, 01033, Ukraine; email: kokozay@univ.kiev.ua, Referenc...

The use of the mononuclear species (NBu(4))(2)[Re(IV)Cl(4)(ox)] (NBu(4)(+) = tetra-n-butylammonium cation; ox = oxalate dianion) as a ligand toward fully solvated divalent first-row transition-metal ions affords the tetranuclear complexes (NBu(4))(4)[{Re(IV)Cl(4)(mu-ox)}(3)M(II)] with M = Mn (1), Fe (2), Co (3), Ni (4), and Cu (5). Their structure...

A general approach to the problem of electron delocalization in the high-nuclearity mixed-valence (MV) clusters containing an arbitrary number of localized spins and itinerant electrons is developed. Along with the double exchange, we consider the isotropic magnetic exchange between the localized electrons as well as the Coulomb intercenter repulsi...