Mind the gap: A complete, cooperative spin transition for a mononuclear Mn(III) complex is reported with an 8 K hysteresis window. Raman spectra collected at a single temperature in warming and cooling modes confirm the electronic bistability within the hysteresis loop. The source of the cooperativity is a disconnection in the hydrogen-bonded 1D chains that connect adjacent cations owing to an order-disorder transition in the PF(6)(-) counterion.

We investigate if the functionality of spin crossover molecules is preserved when they are assembled into an interfacial device structure. Specifically, we prepare and investigate gold nanoparticle arrays, into which room-temperature spin crossover molecules are introduced, more precisely, [Fe(AcS-BPP)2](ClO4)2, where AcS-BPP = (S)-(4-{[2,6-(dipyrazol-1-yl)pyrid-4-yl]ethynyl}phenyl)ethanethioate (in short, Fe(S-BPP)2). We combine three complementary experiments to characterize the molecule-nanoparticle structure in detail. Temperature-dependent Raman measurements provide direct evidence for a (partial) spin transition in the Fe(S-BPP)2-based arrays. This transition is qualitatively confirmed by magnetization measurements. Finally, charge transport measurements on the Fe(S-BPP)2-gold nanoparticle devices reveal a minimum in device resistance versus temperature, R(T), curves around 260-290 K. This is in contrast to similar networks containing passive molecules only that show monotonically decreasing R(T) characteristics. Backed by density functional theory calculations on single molecular conductance values for both spin states, we propose to relate the resistance minimum in R(T) to a spin transition under the hypothesis that (1) the molecular resistance of the high spin state is larger than that of the low spin state and (2) transport in the array is governed by a percolation model.

Dynamic spin interchange where crystals explode with preservation of magnetic memory is observed for a mononuclear hysteretic Fe(iii) Schiff-base compound.

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Thermal spin crossover (SCO) was induced in a high-spin Fe III complex by alkylation of the polyamino ligand backbone. The SCO profile was responsive to chain length with partial crossover observed with C 6 alkylation and full transi-

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Spin crossover [1] (SCO) is an important example of molecular switching, [2] which can be realized by a wide variety of external stimuli. [3][4][5][6] Many applications have been explored, including sensor [7] and display [8] technologies, and data storage. [9] Much effort has been expended to develop the assembly of SCO complexes in materials and impressive results have been achieved with monodisperse nanoparticles, [10] nanocrystals, [11] thin films, [12] micro-and nanopatterned media, [13] Langmuir-Blodgett (LB) films, [14] and hysteretic soft-media assemblies. [15] Progress in this area was recently reviewed by Bousseksou et al., and the link between size morphology and switching characteristics was also examined. [16] However a striking absence from this list is the 1D nanowire. Magnetic nanowires [17] have been cited by the magnetic recording industry as being important in overcoming difficulties in domain wall motion, [18] and reliable thin-film etching [18b, 19] and template-assisted electrodeposition [20] routes to nanowires of magnetic metals have been established. However, preparation of nanowires of functional molecules by such methods is not possible, and wet chemistry routes are better employed. Melt-assisted template assembly methods have been effective for polymers [21] and in favorable cases, nanowires of functional polymers show novel optical properties, including wave guiding [22] and lasing. [23] These nanowires are prepared by adding molten polymer to a nano-porous template, such as anodic aluminum oxide (AAO), followed by acidic or basic template dissolution. Preparation of polymer nanowires is also possible by using solutionassisted template wetting, [24] and this method can be extended to include small molecules, [25] but the acidic or basic treatment means that it is less suitable for fragile small molecules that would not survive dissolution of the template. However, by appropriate modification, insolubility in acids or bases may be conferred on functional small molecules such as mononuclear SCO complexes. To this end, we have investigated the potential of alkylated derivatives [26] of Wilsons [Fe(sal 2trien)] [27] complex, where sal 2 trien is the hexadentate N 4 O 2 bisimino ligand formed by condensation of salicylaldehyde with N 1 ,N 2 -bis(2-aminoethyl)-1,2-ethanediamine, to form nanowires by template assembly in nanoporous AAO, and describe herein the first reported SCO nanowires formed from [Fe III L](BF 4 ) 0.8 Br 0.2 (1).Alkylated ligand L was prepared by substitution of the amines on sal 2 trien with 1-bromododecane, [28] and crystallization in the presence of Fe(BF 4 ) 2 ·6 H 2 O produced the mixed anion salt 1 with some bromide remaining from the ligand synthesis. Structural analysis of rod-shaped crystals of 1 showed packing by intercalation of the ligand C 12 chains (Figure 1), and close association of the coordination centers Figure 1. Molecular structure of 1, and structure of 1 at 100 K showing intercalation of C 12 ligand chains and p-p interactions between phen...

New amphiphilic and spin-labile Mn III complexes based on dianionic N 4 O 2 -hexadentate sal 2 trien or sal 2 bapen ligands were prepared that contain OC 6 H 13 , OC 12 H 25 , or OC 18 H 37 alkoxy substituents at different positions of the salicylidene unit (H 2 sal 2 trien = N,N'' '-bis(salicylidene)-1,4,7,10-tetraazadecane, 10 H 2 sal 2 bapen = N,N'' '-bis(salicylidene)-1,5,8,12-tetraazadodecane). According to electrochemical measurements, these complexes undergo two (quasi)reversible redox processes. Temperaturedependent magnetic measurements revealed a high-spin configuration for all sal 2 trien complexes (S = 2) and gradual spin crossover for sal 2 bapen complexes from high to low spin (S = 1). The chain length strongly influences the spin crossover, as C 18 -functionalization stabilizes the low spin state 15 at much higher temperature than shorter alkyl chains. Moreover, long alkyl chains allow for spontaneous self-assembly of the molecules, which was investigated in single crystals and in Langmuir-films at the air-water interface. Long alkyl chains (C 12 or C 18 ) as well as a mutual synorientation of these molecular recognition sites were required for the Langmuir monolayers to be stable.