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A family of heteroleptic spin crossover (SCO) [FeIII(qsal-5-I)(qsal-5-OMe)]A·sol (qsal-5-X = 5-X-2-[(8-quinolylimino)methyl]phenolate; A = NO3−1 sol = 2MeOH, NCS−2 sol = 0.75MeOH·1.3H2O, BF4−3 sol = MeOH, OTf−4, sol = MeOH) complexes have been synthesized. Most of the complexes exhibit gradual SCO, with the exception of NCS, which is principally high spin. In contrast, the OTf complex shows an abrupt hysteretic SCO (35 K) after solvent loss. The magnetic properties of this complex are significantly improved in comparison to the related homoleptics, [Fe(qsal-I)2]OTf 5 (hysteresis, 8 K) and [Fe(qsal-5-OMe)2]OTf·CH2Cl26 (gradual SCO). Structural studies reveal that slight changes in the crystal packing cause stronger interactions improving the cooperativity. These findings are supported by DFT calculations using the r2SCAN functional in which the calculated structures show that SCO from the LS to the HS state causes pronounced scissoring of the 1D π–π chains and substantial changes in their relative orientation following loss of MeOH. [ABSTRACT FROM AUTHOR]

A series of three solvates [Fe(naphPren)2]I·CH2Cl21, [Fe(naphPren)2]I·CHCl32 and [Fe(naphPren)2]I·acetone 3 with the novel ligand HnaphPren {2-([(2-(propylamino)ethyl]imino)methyl)naphthalen-2-ol} is reported. Magnetic studies of these complexes reveal that 1 exhibits an abrupt SCO at 162 K, whereas 2 possesses a more gradual SCO centred at 172 K. 3 is trapped in the HS state, but irradiation at 980 nm enables accessibility to a hidden LS state via reverse-LIESST. The structures of 1–3 reveal that 1 and 2 show reversible disorder in the propyl group that is coupled to SCO which is absent in the acetone solvate. This study demonstrates how solvent subtly alters the packing impacting the potential flexibility of the propyl chain and thereby switching SCO on or off. [ABSTRACT FROM AUTHOR]

Sildenafil is a specific inhibitor of the phosphodiesterase type 5 (PDE-5) enzyme that protects cyclic guanosine monophosphate from breakdown by PDE-5. It is a biopharmaceutical categorization system Class II medication with low bioavailability because it is almost insoluble in water. The objectives of this study were to prepare sildenafil cocrystals with co-former molecules including aspirin (acetylsalicylic acid [ASA]), fumaric acid (FMA), and benzoic acid (BZA) to improve the water solubility of sildenafil. The cocrystals were prepared by antisolvent addition (AA) and slow solvent evaporation (SE) methods. The stoichiometric ratios of sildenafil and co-former molecules were varied. The obtained crystals were characterized by stereomicroscope, Fourier transformed infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and powder X-ray diffraction (PXRD). The water solubility of sildenafil cocrystals was compared with sildenafil base. In the AA method, the crystals only form in sildenafil-ASA reaction. These crystals were not cocrystals between sildenafil and ASA because they were formed to new substances that were confirmed by single-crystal X-ray diffraction. In the SE method, the cocrystals were successfully prepared in the reaction of sildenafil with ASA, FMA, and BZA which use acetone or ethyl acetate as a solvent. The obtained crystals are irregular shapes and their FT-IR, NMR, and PXRD results exhibited the characteristics of sildenafil and its co-former. The stoichiometric ratios of sildenafil and co-formers after cocrystallization were different from an initial of crystallization. The sildenafil cocrystals with ASA, FMA, and BZA by SE method had higher water solubility than sildenafil base. The sildenafil-FMA cocrystals had the highest water solubility and increased up to five times when compared with sildenafil base. [ABSTRACT FROM AUTHOR]

The influence of the halogen substituent on crystal packing and redox properties is investigated in a series of heteroleptic complexes [Fe(qsal-X)(dipic)]·MeOH (qsal-X = 4-halogen-2-[(8-quinolylimino)methyl]phenolate; dipic = 2,6-pyridinedicarboxylate; X = F 1, Cl 2, Br 3 and I 4). Compounds 1 and 2 exhibit triclinic symmetry (P1¯), whereas 3 and 4 crystallise in monoclinic P21/n. The crystal packing shows self-sorting of the ligands with π-π interactions between the qsal-X ligands and overlap of the dipic ligands to form a 1D chain, that is supported by C–H⋯O interactions. In 1 and 2, the cross-section of the 1D chain is square, while for 3 and 4, it is rectangular. In the former, the dipic ligands interact through C＝O⋯π interactions, while π–π interactions are found in 3 and 4. Neighbouring chains are connected via π–π interactions involving the quinoline rings, but their relative position is driven by the preference of 1 and 2, for C–H⋯X interactions, whereas 3 and 4 form O⋯X halogen bonds. The nature and topology of the electron density of these interactions have been investigated using molecular electrostatic potential (MEP) mapping, quantum theory of atoms in molecules (QTAIM) and 'non-covalent interactions' (NCI) analysis. UV-visible experiments show LMCT bands associated with the qsal-X ligands, confirming the structure is stable in solution. Electrochemical studies reveal slight tuning of the Fe3+/Fe2+ redox couple showing a linear relationship between E°′ and the Hammett parameter σp. [ABSTRACT FROM AUTHOR]

A series of Fe(II) complexes (1–4) and Fe(III) complexes (5–8) from Fe(II)/(III) chloride and N-(8-quinolyl)-X-salicylaldimine Schiff base ligands (Hqsal-X2/X: X = Br, Cl) were successfully synthesized and characterized by spectroscopic (FT-IR, 1H-NMR), mass spectrometry, thermogravimetric analysis (TGA), and single crystal X-ray crystallographic techniques. The interaction of complexes 1–8 with calf thymus DNA (CT-DNA) was determined by UV–Vis and fluorescence spectroscopy. The complexes exhibited good DNA-binding activity via intercalation. The molecular docking between a selected complex and DNA was also investigated. The in vitro anticancer activity of the Schiff base ligands and their complexes were screened against the A549 human lung adenocarcinoma cell line. The complexes showed anticancer activity toward A549 cancer cells while the free ligands and iron chloride salts showed no inhibitory effects at 100 µM. In this series, complex [Fe(qsal-Cl2)2]Cl 6 showed the highest anticancer activity aginst A549 cells (IC50 = 10 µM). This is better than two well-known anticancer agents (Etoposide and Cisplatin). Furthermore, the possible mechanism for complexes 1–8 penetrating A549 cells through intracellular ROS generation was investigated. The complexes containing dihalogen substituents 1, 2, 5, and 6 can increase ROS in A549 cells, leading to DNA or macromolecular damage and cell-death induction. [ABSTRACT FROM AUTHOR]

OctaDist is an interactive and visual program for determination of structural distortion in octahedral coordination complexes such as spin crossover complexes, single-ion magnets, perovskites or metal–organic frameworks. OctaDist computes the octahedral distortion parameters initially designed in the context of the spin-crossover phenomenon and denoted ζ, Σ, and Θ from standard structural files. The program also provides additional tools for molecular analyses and visualization. It emphasizes performance, flexibility, ease of use, application programming interface (API) consistency, and clear documentation. The modules and classes in OctaDist can be easily customized to include new algorithms or analytical tools. OctaDist is cross-platform supported for modern operating systems and is available as open-source distributed under the GNU General Public License version 3. [ABSTRACT FROM AUTHOR]

Two conformational polymorphs of (N,N‐dibutyldithiocarbamato‐κ2S,S′)[tris(3,5‐diphenylpyrazol‐1‐yl‐κN2)hydroborato]cobalt(II), [Co(C45H34BN6)(C9H18NS2)] or [TpPh2Co(S2CNBu2)], 1, are accessible by recrystallization from dichloromethane–methanol to give orthorhombic polymorph 1a, while slow evaporation from acetonitrile produces triclinic polymorph 1b. The two polymorphs have been characterized by IR spectroscopy and single‐crystal X‐ray crystallography at 150 K. Polymorphs 1a and 1b crystallize in the orthorhombic space group Pbca and the triclinic space group P, respectively. The polymorphs have a trans (1a) and cis (1b) orientation of the butyl groups with respect to the S2CN plane of the dithiocarbamate ligand, which results in an intermediate five‐coordinate geometry for 1a and a square‐pyramidal geometry for 1b. Hirshfeld surface analysis reveals minor differences between the two polymorphs, with 1a exhibiting stronger C—H...S interactions and 1b favouring C—H...π interactions. [ABSTRACT FROM AUTHOR]

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Three iron(III) complexes, [Fe(qnal)2]Y {qnal = 1‐[(8‐quinolinylimino)methyl]‐2‐naphthalenolate; Y = NO31, BPh4·CH2Cl22, NCS 3} have been prepared to explore anion effects in spin crossover systems. Structural studies on 2 reveal supramolecular chains formed by π–π and C–H···π interactions between the [Fe(qnal)2]+ cations. Magnetic susceptibility measurements show the onset of spin crossover in 1 above 200 K, while complete spin crossover is observed in 2 and 3 with T1/2 = 285 and 340 K, respectively. Unusually, 2 also undergoes light‐induced excited spin state trapping (LIESST) at 980 nm with ca. 65 % efficiency and T(LIESST) = 25 K and reverse‐LIESST at 660 nm with full reversibility over many cycles. The results highlight the important influence that the anion has on thermal and light‐activated spin crossover properties. [ABSTRACT FROM AUTHOR]

Two iron(III) spin crossover complexes, [Fe(qsal-X)2]OTs·nH2O, (Br 1·H2O; I, 2·2H2O or non-solvated 1, 2) have been prepared and fully characterized. Structural studies of 1·H2O and 2·2H2O reveal the presence of 1D π–π chains linking the Fe(III) centres and a strong X⋯O halogen bond. In both complexes the 1D π–π chains are angled relative to each other, enforced by C–H⋯X interactions. Magnetic studies reveal abrupt spin crossover in 1 (T1/2↓ = 258 K and T1/2↑ = 260 K) and 2 (T1/2 = 298 K) with T1/2 increasing on going from Br to I. The presence of abrupt spin crossover in both complexes shows that aromatic anions can be effective in the design of cooperative spin crossover systems. [ABSTRACT FROM AUTHOR]

Molecular magnetic switches are expected to form the functional components of future nanodevices. Herein we combine detailed (photo‐) crystallography and magnetic studies to reveal the unusual switching properties of an iron(III) complex, between low (LS) and high (HS) spin states. On cooling, it exhibits a partial thermal conversion associated with a reconstructive phase transition from a [HS‐HS] to a [LS‐HS] phase with a hysteresis of 25 K. Photoexcitation at low temperature allows access to a [LS‐LS] phase, never observed at thermal equilibrium. As well as reporting the first iron(III) spin crossover complex to exhibit reverse‐LIESST (light‐induced excited spin state trapping), we also reveal a hidden hysteresis of 30 K between the hidden [LS‐LS] and [HS‐LS] phases. Moreover, we demonstrate that FeIII spin‐crossover (SCO) complexes can be just as effective as FeII systems, and with the advantage of being air‐stable, they are ideally suited for use in molecular electronics. [ABSTRACT FROM AUTHOR]

Molecular magnetic switches are expected to form the functional components of future nanodevices. Herein we combine detailed (photo‐) crystallography and magnetic studies to reveal the unusual switching properties of an iron(III) complex, between low (LS) and high (HS) spin states. On cooling, it exhibits a partial thermal conversion associated with a reconstructive phase transition from a [HS‐HS] to a [LS‐HS] phase with a hysteresis of 25 K. Photoexcitation at low temperature allows access to a [LS‐LS] phase, never observed at thermal equilibrium. As well as reporting the first iron(III) spin crossover complex to exhibit reverse‐LIESST (light‐induced excited spin state trapping), we also reveal a hidden hysteresis of 30 K between the hidden [LS‐LS] and [HS‐LS] phases. Moreover, we demonstrate that FeIII spin‐crossover (SCO) complexes can be just as effective as FeII systems, and with the advantage of being air‐stable, they are ideally suited for use in molecular electronics. [ABSTRACT FROM AUTHOR]

Molecular magnetic switches are expected to form the functional components of future nanodevices. Herein we combine detailed (photo‐) crystallography and magnetic studies to reveal the unusual switching properties of an iron(III) complex, between low (LS) and high (HS) spin states. On cooling, it exhibits a partial thermal conversion associated with a reconstructive phase transition from a [HS‐HS] to a [LS‐HS] phase with a hysteresis of 25 K. Photoexcitation at low temperature allows access to a [LS‐LS] phase, never observed at thermal equilibrium. As well as reporting the first iron(III) spin crossover complex to exhibit reverse‐LIESST (light‐induced excited spin state trapping), we also reveal a hidden hysteresis of 30 K between the hidden [LS‐LS] and [HS‐LS] phases. Moreover, we demonstrate that FeIII spin‐crossover (SCO) complexes can be just as effective as FeII systems, and with the advantage of being air‐stable, they are ideally suited for use in molecular electronics. [ABSTRACT FROM AUTHOR]

A series of iron(iii) complexes [Fe(naphEen)2]X·sol (naphEen = 1-{[2-(ethylamino)-ethylimino]methyl}-2-naphtholate; X = F, sol = 0.5CH2Cl2·H2O 1; sol = H2O, X = Cl, 2 and X = Br 3) and [Fe(naphEen)2]I 4 has been prepared. The UV-Vis spectra reveal clear differences for 1 which DFT/TDDFT calculations suggest are due to an equilibrium between [Fe(naphEen)2]F and [Fe(naphEen)2F], the latter having a coordinated F ligand. The X-ray crystal structures of 2–4 show LS Fe(iii) centres in all cases and extensive aryl interactions that link the Fe centres into supramolecular squares. In 3 at room temperature the compound loses half an equivalent of water resulting in a change in space group from Monoclinic P21/n to C2/c. Magnetic studies indicate that 1 is trapped in a mixed spin state being ca. 40% HS while 2–4 are effectively low spin up to 350 K. In contrast, Mössbauer spectroscopic studies of 1 indicate a gradual but incomplete spin crossover. The magnetic properties of 2–4 contrast with the related [Fe(salEen-X)2]anion derivatives which are often spin crossover active. [ABSTRACT FROM AUTHOR]

A unique self-assembled mixed-valence FeII–FeIII tetranuclear star has been comprehensively characterised showing a large magnetic anisotropy at the peripheral FeII centres, ferromagnetic coupling between the iron centres and field-induced SMM behaviour. [ABSTRACT FROM AUTHOR]

Reaction of a rigid tridentate ligand o-[(1H-imidazol-2-yl)methylideneamino]phenol (2-H2imap) with Co(ClO4)2 in the presence of NaN3, or Co(NO3)2 without a base yields [CoII(2-Himap)2] 1 and [CoIII(2-Himap)2]NO3·MeOH 2, respectively. Both complexes exhibit a mer-octahedral geometry with the cobalt centre being distorted along an octahedral-trigonal prismatic pathway. The packing in 1 and 2 is dominated by H-bonding forming 2D sheets and 1D chains, respectively. Detailed dc and ac magnetic studies indicate that 1 is a field-induced single-ion magnet (SIM) with D = 36.7 cm−1 and E = 2.0 cm−1. Extensive ab initio calculations support these conclusions and suggest that relaxation of the magnetization occurs principally through direct quantum tunnelling in the ground state, with the Raman process dominant in an applied field. This contrasts with the recently reported series of mer-[Co(L)2] (L = monoanionic NNO donor ligand; Inorg. Chem., 2017, 56, 6056–6066) complexes where D is negative, as these compounds have a more ambiguous geometry, and highlights the importance of supramolecular interactions in subtly altering the coordination sphere thereby impacting the magnetic behaviour. [ABSTRACT FROM AUTHOR]

Mixed ligand complexes [Fe(qsal-Cl)(qsal-Br)]Y·sol (Y = NCS, sol = MeOH 1; PF62; BPh4, sol = 2CH2Cl23; OTf, sol = 0.5MeOH 4) have been synthesized. X-ray crystallographic studies of 1, 2 and 4 at 123 K reveal that the Fe(iii) centres are low spin in all cases. In 2 there are two independent Fe(iii) centres in the asymmetric unit cell. The structure of 3 has been determined at 100, 123 and 269 K with the Fe centre low spin, mixed spin and mostly high spin, respectively. Packing in the complexes is dominated by π–π interactions which form a 1D chain. C–H…π, C–H…Cl/Br and C–Cl/Br…π interactions link the chains to form highly cooperative supramolecular 3D networks mirroring the homoleptic complexes. SQUID magnetometric studies show almost complete, 50% complete and stepped spin crossover for 1, 2 and 3 respectively. [Fe(qsal-Cl)(qsal-Br)]OTf·0.5MeOH 4 is low spin up to 350 K. Compared to the homoleptic complexes spin crossover behaviour is mostly intermediate between the [Fe(qsal-Cl)2]+ and [Fe(qsal-Br)2]+ systems except for 3 where spin crossover characteristics are improved compared to the homoleptic complexes. [ABSTRACT FROM AUTHOR]

A new air stable FeIII spin crossover (SCO) complex has been synthesized. The compound undergoes abrupt SCO near room temperature with T1/2 (↓) = 244 K and T1/2 (↑) = 278 K. Structural studies of the complex in the high spin and low spin state show that the strong cooperativity and thus the wide hysteresis is driven by an unprecedented anionic conformational change. [ABSTRACT FROM AUTHOR]

A detailed investigation of the accuracy of different quantum mechanical methods for the study of iron(III) spin crossover complexes is presented. The energy spin state gap between the high and low spin states; Δ E(HS-LS) of nine iron(III) quinolylsalicylaldiminate complexes were calculated with nine different DFT functionals, then compared. DFT functionals: B3LYP, B3LYP-D3, B3LYP*, BH&HLYP, BP86, OLYP, OPBE, M06L, and TPSSh were tested with six basis sets: 3-21G*, dgdzvp, 6-31G**, cc-pVDZ, Def2TZVP, and cc-pVTZ. The cations from the X-ray crystal structures of [Fe(qsal-OMe)2]Cl·MeCN·H2O, [Fe(qsal-OMe)2]Cl·2MeOH·0.5H2O, [Fe(qsal-OMe)2]BF4·MeOH, [Fe(qsal-OMe)2]NCS·CH2Cl2, [Fe(qsal-F)2]NCS, [Fe(qsal-Cl)2]NCS·MeOH, [Fe(qsal-Br)2]NCS·MeOH, [Fe(qsal-I)2]OTf·MeOH, and [Fe(qsal)2]NCS⋅CH2Cl2 were used as starting structures. The results show that B3LYP, B3LYP-D3, OLYP, and OPBE with a 6-31G**, Def2TZVP, and cc-pVTZ basis set give reasonable results of Δ E(HS-LS) compared with the experimental data. The enthalpy of [Fe(qsal-I)2]+ calculated with an OLYP functional and cc-pVTZ basis set (1.48 kcal/mol) most closely matches the experimental data (1.34 kcal/mol). B3LYP* yields an enthalpy of 5.92 kcal/mol suggesting it may be unsuitable for these Fe(III) complexes, mirroring recent results by Kepp ( Inorg. Chem., 2016, 55, 2717-2727). [ABSTRACT FROM AUTHOR]

The new ligand Hqsal-4-OMe was synthesized, and four iron(III) complexes, [Fe(qsal-4-OMe)2]Y ·CH2Cl2 [Hqsal-4-OMe = 4-methoxy- N-(8-quinolyl)salicylaldimine; Y = ClO4 ( 1), NO3 ( 2)] and [Fe(qsal-4-OMe)2]Y (Y = PF6 ( 3), OTf ( 4)] as well as the isomer [Fe(qsal-5-OMe)2]PF6 ·CH2Cl2 ( 5), were prepared. UV/Vis spectroscopic studies indicated that the complexes are high-spin in solution and exhibit a ligand-to-metal charge-transfer band around 400 nm. X-ray crystallographic studies on [Fe(qsal-4-OMe)2]Y ·CH2Cl2 (Y = ClO4, NO3) and [Fe(qsal-4-OMe)2]PF6 at 97 K revealed high-spin FeIII centres with one of the qsal-4-OMe ligands significantly distorted from planarity. In contrast, in 5 the FeIII centre is low-spin at low temperature, and the room-temperature structure of 5 shows about 25 % spin crossover (SCO). The structure of [Fe(qsal-4-OMe)2]Y ·sol shows weak π-π interactions between neighbouring cations, while 5 exhibits stronger π-π interactions that link it into a 1D chain. SQUID magnetometric studies revealed that 1- 4 are essentially high-spin, whereas 5 undergoes gradual and almost complete SCO up to 350 K. A combination of distortions to the qsal-4-OMe ligand and intermolecular C-H ···O interactions involving both the coordinated phenolate oxygen atom and the OMe group seem to be responsible for the loss of SCO. [ABSTRACT FROM AUTHOR]

The liquid-air interface is demonstrated as a method to assemble nanoparticles synthesized from the reaction between iron (III) dibenzoylmethane (Fe(dbm)) and platinum acetylacetonate (Pt(acac)) into a long range monolayer. These surface-modified particles have average Fe to Pt atomic ratio of 0.77:1. The increase in surfactants further reduces the Fe:Pt ratio and increases the particle diameter to over 4 nm. The self-assembled pattern of FePt-based nanoparticles can be enhanced by dropping nanoparticle suspensions on the surface of diethelyne glycol (DEG). The concentrations of these nanoparticle suspensions in hexane from 0.2 to 0.4 mg/ml can be used without the agglomeration into multilayered islands. The voids in the self-assembled monolayer on the DEG-air interface are reduced to the minimum in the case of the lowest concentration. [ABSTRACT FROM AUTHOR]

[Fe(qsal-Br)2]NO3·2MeOH is reported which undergoes abrupt two step symmetry breaking spin crossover, T½(1st step) = 136 K and T½(2nd step) = 232 K with a hysteresis of 16 K and 5 K, respectively, and an unprecedented [HS–LS] plateau of 96 K. [ABSTRACT FROM AUTHOR]

Two new MnII/III redox pairs, [Mn(qsal-Cl)2]0/+ 10/+ and [Mn(qsal-Br)2]0/+ 20/+ have been synthesized employing the tridentate Schiff base ligands, 5-X- N-(8-quinolyl)salicylaldimine (Hqsal-X, X = Cl and Br). The neutral MnII complexes 1 and 2 were prepared from MnCl2 and Hqsal-Cl and Hqsal-Br while oxidation of 1 or 2 with AgOTf yields the cationic MnIII complexes, [Mn(qsal-Cl)2]OTf, 1+, and [Mn(qsal-Br)2]OTf, 2+. 1 and 2 have been characterized by single-crystal X-ray diffraction as CH2Cl2 solvates. The Mn centres adopt a strongly distorted octahedral geometry with cis O donors due to the pair of meridionally bound qsal-X ligands. Electrochemical studies indicate two reversible one-electron redox processes, Mn2+/3+ and Mn3+/4+. Spectroscopic studies show the LMCT bands move to lower wavelengths by ca. 30 nm while the νC=N stretches are little changed in the cationic complexes. Variable temperature magnetic susceptibility measurements indicate that 1+ and 2+ undergo gradual half spin crossover, despite having cis O donors. DFT calculations reveal a small HS-LS gap in the MnIII systems consistent with spin crossover and provide insight into the ligand design necessary for spin crossover in cis-N4O2 MnIII compounds. [ABSTRACT FROM AUTHOR]

The reaction of H2salpn(H2salpn = N,N'-bis(salicylidene)-1,3-propanediamine)withFe(ClO4)3 in a ratio of 1:1 and 3 :2, leads to dark red crystals of the solvatomorphs [(salpn)Fe(m2-salpn)Fe(salpn)]-0.5MeOH (1) and [(salpn)Fe(p.2-salpn) Fe(salpn)]-MeOH (2), respectively. X-Ray crystallographic studies reveal a slightly distorted octahedral geometry and meridional configuration of the N and O donor atoms with one of the salpn ligands acting as a bridge between the two FeIII atoms to create a dimer. The Fe-N/O bond distances for both dimers indicate that the Fe centres are high spin. Supramolecular dimeric pairs are formed in both structures from C-H … π and/or C-H…O interactions. However, the degree of solvation significantly impacts the arrangements of these dimeric pairs with tightly packed 1D chains in 2 and more loosely packed chains in 1. In addition, electrochemical studies reveal weak communication between the two Fe atoms despite the large distance between them and the lack of conjugation across the bridge. [ABSTRACT FROM AUTHOR]

By implementing transmission electron microscope (TEM) image processing, effects of a reducing agent and surfactant concentrations on the reactions between Pt(acac) and alternative Fe( β-diketonate) , i.e., Fe(tmhd) and Fe(hfac) , can be determined. The oleic acid and oleylamine of 0.5 mmol give rise to the FePt-based nanoparticles as small as 3 nm. Larger particles up to 5 nm in diameter with better self-assembled patterns are obtained by increasing each surfactant to 5 mmol. With such excessive surfactants in the synthesis, the reducing agent such as 1,2-hexadecanediol may not be required since it does not significantly influence the particle size and assembly. Moreover, it accelerates the reduction of Pt(acac) , resulting in larger size distribution. This work demonstrates that image processing allows the size analysis from statistically sufficient number of nanoparticles. This intensity-based analysis is, however, susceptible to the error arising from a low contrast between the nanoparticle and the background. The magnification of TEM images should therefore be optimized to minimize systematic errors. [ABSTRACT FROM AUTHOR]

Three novel copper hydrotris(3,5-diphenylpyrazolyl)borate (TpPh2) dithiocarbamate complexes, [TpPh2Cu(dtc)] (dtc = S2CNEt21, S2CNBz22 and S2CN(CH2)43) have been prepared in a simple one pot reaction by sequential addition of KTpPh2 and Na(dtc) to CuCl2·2H2O. IR, UV-Vis and ESR spectroscopic studies suggest a mostly κ3 coordinated TpPh2 ligand, bidentate dithiocarbamate ligands and therefore, a five coordinate copper centre. Unusually, a κ3 to κ2 isomerisation of the TpPh2 ligand is found in solution in 3 and to a lesser extent in 1. The X-ray crystal structures reveal geometries intermediate between trigonal bipyramidal and square pyramidal depending on the steric bulk of the dithiocarbamate ligand and a long Cu–N bond resulting in an asymmetrically bound TpPh2 ligand. Electrochemical studies reveal quasi-reversible one-electron oxidation and reduction to Cu(i) with the reversibility and reduction potential strongly dependent on the dithiocarbamate. DFT calculations reveal a weakly antibonding Cu–S π* SOMO and a strongly antibonding Cu–S σ* LUMO consistent with the significant effect of the dithiocarbamate ligand on the electrochemical behaviour of these complexes. [ABSTRACT FROM AUTHOR]

The reaction of Fe(NCS)3 prepared in situ in MeOH with Hqsal-X (Hqsal-X = 5-X-N-quinolylsalicylaldimine) in CH2Cl2 yields the FeIII complexes, [Fe(qsal-X)2]NCS·solvent (X = F 1; X = Cl, 2, Br, 3 solvent = MeOH; X = I, solvent = 0.25CH2Cl2·0.5MeOH 4) in moderate to good yields. IR spectroscopy confirms that NCS- acts as a counteranion only and that the qsal-X ligand is bound to the FeIII centre. SQUID magnetometric studies reveal stepped hysteretic spin crossover in 1 and 2, which is abrupt in both steps in latter compound. Mössbauer spectroscopic studies of 1 and 2 support these conclusions. The bromo derivative, 3, undergoes half spin crossover up to 340 K while 4 is low spin at all temperatures measured. The spin transition temperature, T1/2 is found to increase on moving from F to Br. UV-Vis and NMR spectroscopic studies indicate that 1-4 have spin states intermediate between HS and LS in solution. Structural studies show that 1, 2 and 3 crystallize in triclinic P1 while 4 is in monoclinic P21/c. Crystallographic studies of 1 at 100, 200 and 270 K show that spin crossover proceeds from a [LS-LS] state through a [LS-HS] intermediate to a [HS-HS] state (LS = low spin, S = 1/2, HS = high spin, S = 5/2). Similar results are found for 3 although this time a [LS-IS] state exists at 123 K while a [LS-HS] state is found at 295 K (IS = intermediate spin state where partial spin crossover has occurred). Both 2 and 4 are found to have LS FeIII centres although the latter contains two crystallographically independent FeIII centres in the asymmetric unit. The crystal packing in 1-4 consists of extensive π-π interactions through the planar qsal-X ligands and CH...X (X = O, halogen) and/or X...π (X = halogen) interactions which result in pseudo 3D supramolecular networks. This results in high cooperativity in 1 and 2 and is probably responsible for the hysteretic stepped spin crossover in these compounds. [ABSTRACT FROM AUTHOR]

A new sterically bulky Schiff base ligand, N-(8-quinolyl)-5-tert-butylsalicylaldimine (Hqsal-5-tBu) has been prepared and a series of FeIII complexes, [Fe(qsal-5-tBu)2]Y (Y = Cl 1, ClO4 2, NO3 3, BF4 4) utilising this ligand are reported and fully characterised. UV-vis spectroscopic and electrochemical studies indicate that 1-4 are high spin (HS) in solution at room temperature and further suggest that the tBu group only slightly alters the electronic properties of 1-4 compared with related [Fe(qsal-5-X)2+ systems. The structures of [Fe(qsal-5-tBu)2]Cl x 4MeOH x H2O 1, [Fe(qsal-5-tBu)2]ClO4 x MeOH 2, and [Fe(qsal-5-tBu) 2]NO3 3 determined at 100 K reveal HS FeIII centres in all cases. Four-fold parallel aryl embraces and π-π interactions serve to link the cations forming 2D sheets mirroring the motifs found in other [Fe(qsal-5-X)2]+ complexes. Despite this the tBu group causes strong distortions at the Fe centre which as magnetic studies reveal prevent spin crossover trapping 1-4 in the HS state. A novel ligand, N-(8-quinolyl)-5-tert-butylsalicylaldimine (Hqsal-5-tBu) is prepared and a series of FeIII complexes, [FeIII(qsal-5-tBu)2+ studied. Strong structural distortions caused by the ligand result in the complexes becoming trapped in the high spin state. [ABSTRACT FROM AUTHOR]

A series of FeIII complexes, [Fe(qsal-5-OMe)2]Y [Y = BF4 ( 1), PF6 ( 2), NCS ( 3), BPh4 ( 4)], have been prepared and structurally and magnetically characterized. The low-temperature structures of 1 and 3 as solvent adducts were determined by X-ray crystallography with LS FeIII centres found in both cases. π-π and C-H ···π interactions between the cations lead to 2D sheets that are linked to one another through C-H ···O and, in the case of 3, C-H ···N/S interactions resulting in high cooperativity. Magnetic studies revealed abrupt and gradual spin crossover for 3 and 2, respectively. For 3, spin crossover with possible thermal hysteresis was observed although solvent loss (CH2Cl2) could occur. In contrast, 1 and 4 were found to be low and high spin only, respectively. The results of Mössbauer spectroscopic studies are consistent with the magnetic susceptibility data and indicate that there are two low-spin FeIII centres in 2. Finally, electrochemical studies showed reversible reduction to FeII at -0.22 V, whereas reversible oxidation of the qsal-5-OMe ligand was found to occur between 1.04-1.06 V. [ABSTRACT FROM AUTHOR]

A new synthesis of (8-quinolyl)-5-methoxysalicylaldimine (Hqsal-5-OMe) is reported and its crystal structure is presented. Two FeIII complexes, [Fe(qsal-5-OMe)2]Cl ⋅solvent (solvent=2 MeOH ⋅0.5 H2O ( 1) and MeCN ⋅H2O ( 2)) have been prepared and their structural, electronic and magnetic properties studied. [Fe(qsal-5-OMe)2] Cl ⋅2 MeOH ⋅0.5 H2O ( 1) exhibits rare crystallographically independent high-spin and low-spin FeIII centres at 150 K, whereas [Fe(qsal-5-OMe)2]Cl ⋅ MeCN ⋅H2O ( 2) is low spin at 100 K. In both structures there are extensive π-π and CH⋅⋅⋅π interactions. SQUID magnetometry of 2 reveals an unusual abrupt stepped-spin crossover with T1/2=245 K and 275 K for steps 1 and 2, respectively, with a slight hysteresis of 5 K in the first step and a plateau of 15 K between the steps. In contrast, 1 is found to undergo an abrupt half-spin crossover also with a hysteresis of 10 K. The two compounds are the first FeIII complexes of a substituted qsal ligand to exhibit abrupt spin crossover. These conclusions are supported by 57Fe Mössbauer spectroscopy. Both complexes exhibit reversible reduction to FeII at −0.18 V and irreversible oxidation of the coordinated qsal-5-OMe ligand at +1.10 V. [ABSTRACT FROM AUTHOR]

The synthesis of trans-[Ni(dbm)(RN=C(Me)NHR)] (dbm = 1,3-diphenylpropanedionate; R = phenyl, p-tolyl, 3,5-dimethylphenyl, 3,5-dichlorophenyl) has been achieved by reaction of [Ni(dbm)(HO)] with two equivalents of the amidine ligands, RN=C(Me)NHR. X-ray crystallographic studies reveal that trans-[Ni(dbm)(RN=C(Me)NHR)] (R = 3,5-dimethylphenyl) exhibits an intramolecular N-H···O hydrogen bond, which along with the large steric bulk of the amidine ligands may enforce the trans geometry. Electrochemical studies show a strong dependence of the oxidation potential on the substituent groups despite their remote position. DFT calculations indicate that the HOMO consists of Ni-ligand π* orbitals with a significant contribution from the amidine ligands. [ABSTRACT FROM AUTHOR]

Mixed ligand tris(pyrazolyl)borate and β-diketonate complexes have been prepared by reacting [TpNiBr] with a β-diketone and then adding 1,8-diazabicycloundec-7-ene to yield [TpNi(β-dkt)] {β-dkt = hexafluoroacetylacetonate (hfac) 1, phenylbutanedionate (pbd) 2, diphenylpropanedionate (dbm) 3, tetramethylheptanedionate (tmhd) 4}. The green solids have been characterized by IR, UV-Vis, and H NMR spectroscopy. Crystallographic studies of [TpNi(dbm)] reveal a five-coordinate, square pyramidal nickel centre with a κ-coordinated Tp ligand and a bidentate β-diketonate ligand. [ABSTRACT FROM AUTHOR]

The cationic complexes, [TpRNi(bpym)]+ {TpR = tris(3,5-diphenylpyrazolyl)borate, R = Ph2 1; tris(3-phenyl-5-methylpyrazolyl)borate, R = Ph,Me 2} were synthesized by reacting [TpRNiBr] (R = Ph2; Ph,Me) with bipyrimidine followed by subsequent addition of KPF6 in CH2Cl2. The green solids have been characterized by IR, UV–Vis and 1H NMR spectroscopy. Crystallographic studies of [TpPh,MeNi(bpym)]PF6 reveal a five-coordinate square pyramidal nickel centre with a κ3-coordinated TpPh,Me ligand and a chelating bipyrimidine ligand. Cyclic voltammetric studies show irreversible reduction with the degree of reversibility dependent on the type of TpR ligand. [ABSTRACT FROM AUTHOR]

The reaction of CoX2 (X = Cl, Br, NO3) with KTpPh2 in tetrahydrofuran (THF) yields the half-sandwich compounds [TpPh2CoX] (X = Cl 1, Br 2, NO3 3). The reaction of [TpPh2CoBr] with NaX (X = N3, NO2) or potassium thiocyanate (KNCS) permits isolation of [TpPh2CoX] (X = N3 4, NCS 5, NO2 6). In contrast, the reaction of cobalt(II) acetate with KTpPh2 yields [TpPh2Co(OAc)(HpzPh2)] 7 as a result of B-N bond cleavage. Subsequent reaction of 7 with a range of β-diketones in the presence of NaOMe produces the β-diketonate complexes, [TpPh2Co(β-diketonate)] (β-diketonate = acac 8, hfac 9, dbm 10, tmhd 11). IR spectroscopy suggests that the TpPh2 ligands are κ³-coordinated and that the β-diketonate ligands adopt a bidentate coordination mode. Electronic spectra are consistent with four- or five-coordinate species in solution. X-Ray crystallographic studies of 7 reveal an intermediate five-coordinate cobalt centre with a hydrogen bonding interaction between the pyrazole hydrogen and the acetate carbonyl oxygen. The molecular structures of 9 and 10 show cobalt centres with square pyramidal coordination geometries and κ²-coordinated β-diketonate ligands. Cyclic voltammetric studies of 6 reveal irreversible one-electron reduction to Co(I). However, the β-diketonate complexes, 8, 10 and 11 undergo irreversible one-electron oxidation. The redox potential and reversibility increases as the steric bulk of the substituent on the β-diketonate ligand increases. [ABSTRACT FROM AUTHOR]

Under microwave activation, triethylorthoacetate reacts with the substituted anilines in the presence of acetic acid as a catalyst, producing acetamidine in moderate to high yields. The X-ray structures of the new amidines, N,N'-bis(3,5-dimethylphenyl)-acetamidine and N,N'-bis(p-tolyl)acetamidine, are also reported, revealing polymeric chains supported by intramolecular H-bonds. [ABSTRACT FROM AUTHOR]

The first Fe(iii) qsal-X complex exhibiting abrupt complete spin crossover at 228 K with a hysteresis of 8 K, [Fe(qsal-I)2]OTf is reported. Structural studies of the MeOH solvate in the LS and HS state and at the spin transition are described. [ABSTRACT FROM AUTHOR]

A series of Fe(II) complexes, fac-[Fe(4-ima-Bp)3](Y)2⋅sol (Y = ClO4; sol = 3EtOH 1, 3MeOH 2; Y= BF4; sol = EtOH⋅4H2O 3, 4H2O 4 and 3.5MeCN 5) have been prepared and structurally and magnetically characterized. The low temperature structures of 1, 2 and 5 have been determined by X-ray crystallography with LS Fe(II) centres found in all cases. Extensive C–H···π interactions between the cations form 2D layers, which are linked to one another through N-H···O and O-H···O hydrogen bonds, resulting in high cooperativity. Despite 5 containing MeCN, N-H···O/F hydrogen bonds, and C–H···π and π-π interactions combine to give similar 2D layers. Magnetic measurements reveal moderately abrupt spin crossover for 1-4; becoming more gradual and only 50% complete in 1 due to solvent loss. The MeCN solvate shows more gradual SCO and reinforces how subtle changes in packing can significantly influence SCO behaviour. [ABSTRACT FROM AUTHOR]

The reaction of bis­(1,3-diphenylpropane-1,3-dionato)cobalt(II), [Co(dbm)2], with bis­(diphenyl­phosphino)ethane (dppe) affords the coordination polymer catena-poly[[bis­(1,3-diphenyl­propane-1,3-dionato-κ2 O, O′)cobalt(II)]-μ-ethyl­enebis(diphenyl­phosphine oxide)-κ2 O: O′], trans-[Co(C15H11O2)2(C26H24O2P2)] n, as a result of oxidation of the diphos­phine. The Co atom is octa­hedral, with a CoO6 coordination sphere, and the chelating dbm ligands adopt a trans configuration. The Co atom also lies on a centre of inversion, with a further symmetry centre bis­ecting the bridging ethyl­enebis(diphenyl­phosphine oxide) ligand. [ABSTRACT FROM AUTHOR]