الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Numerous efforts are devoted to developing new enhanced molecular magnetic materials including single molecule magnets (SMMs) that can meet the requirements for future technologies such as quantum computing and spintronics. One of the current trends in the field is to enhance the global anisotropy in metal complexes using single-ion anisotropy. Furthermore, the rational control of the coordination environmentof metal ions is very crucial in order to ensure larger single ion anisotropies. The work herein describes efforts to synthesize and characterize new cyanide building blocks suitable to incorporate the highly anisotropic early transition metal, V(III) into hetreometallic molecular magnetic materials. It also highlights the importance of tuning the local coordination environments of metal ions in order to achieve enhanced single ion anisotropy.
A family ofmononuclear vanadium (III) compounds with axially distorted coordination environmentof the general formula, A[L3VX3] (3-9) (X = F, Cl or Br, A+ = Et4N+, nBu4N+ or PPN+ , L3 = Tp or Tp*(Tp = tris(-1-pyrazolyl)borohydride), Tp* = tris(3,5-dimethyl-1-pyrazolyl)borohydride)), and [Tp*V(DMF)3](PF6)2were studied. Replacing Tp ligand in 3 with the stronger π donor, Tp*, in resulted in almost doubling the magnitude of the axial zero field splitting parameter D (D = -16.0 cm-1 in 3, and -30.0 cm-1 in 4) as calculated based on magnetic measurements. Such an interesting result introduces the control of axial crystal field distortions as a new route for enhancing single ion anisotropy. The HFEPR measurements on a single crystal of 4 revealed an even higher D value (-40.0 cm-1). Compound 4exhibits evidence for an out-of-phase signal when subjected to ac measurements under 1000 Oe dc field.
A new series of vanadium cyanide building blocks,PPN[V(acac)2(CN)2]∙PPNCl (13) (PPN = , acac = acetylacetonate), A[V(L)(CN)2](A = tetraethylammonium, L = N,N’-Ethylenebis(salicylimine) (14), A = PPN, L = N,N’-Ethylenebis(salicylimine) (15), A = PPN, L = N,N’-Phenylenebis(salicylimine)(16), and A = PPN, L = 2-methoxysalen = N,N’-Ethylenebis(2-methoxysalicylimine)(17)) have been synthesized and structurally characterized. The magnetic studies revealed moderate Dvalues (-10.0, 5.89, 3.7, 4.05 and 4.36 cm-1 for 13-17 respectively).The powders obtained from the reaction of 14 with [Mn(salen)(H2O)](ClO4) were proposed to be [V(salen)(CN)2][Mn(salen)]n (18).Magnetic studies of 18 were interpreted as anantiferromagnetically coupled V-CN-Mn 1D chain(J = -4.4 cm-1). Susceptibility studies of the ac type led to an estimated energy barrier of 13.5 cm-1with τ = 1.52x10-8 s.
Another series of new trigonalbipyramidal (TBP) molecules incorporating the highly anisotropic[(triphos)Re(CN)3]-building block and lanthanides with the general formula (Et4N)2[(Re(triphos)(CN)3)2(Ln(NO3)3)3]∙4CH3CN (19-27) where Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dyand Ho, is presented.Thisseries of compounds chapter represents the first family of cyanide-bridged lanthanide containing TBPs which adds valuable information to our reservoir of compounds with TBP geometry. The SQUID studies of the magnetic properties revealed a variety of magnetic responses. Compound 25 and 26 exhibit slow paramagnetic relaxation of magnetization at zero field below 3 K, indicative of SMM behavior.