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Four acyclic CoII–3LnIII triangle complexes are reported in which two Co ions in each complex are octahedral while the third Co exhibits a lanthanide dependent coordination geometry. Magnetic analysis of the La complex shows a large ZFS effect for Co.

Four new non-macrocyclic triangular Ni3M (M = LaIII, EuIII, GdIII, or BaII) complexes with planar Ni3MO6 cores are reported, including structural and magnetic characterisation.

Iron oxide nanoparticles (IONPs) have gained increasing attention in various biomedical and industrial sectors due to their physicochemical and magnetic properties. In the biomedical field, IONPs are being developed for enzyme/protein immobilization, magnetofection, cell labeling, DNA detection, and tissue engineering. However, in some established areas, such as magnetic resonance imaging (MRI), magnetic drug targeting (MDT), magnetic fluid hyperthermia (MFH), immunomagnetic separation (IMS), and magnetic particle imaging (MPI), IONPs have crossed from the research bench, received clinical approval, and have been commercialized. Additionally, in industrial sectors IONP-based fluids (ferrofluids) have been marketed in electronic and mechanical devices for some time. This review explores the historical evolution of IONPs to their current state in biomedical and industrial applications.

Given the technical hurdles associated with the thermal decomposition method for the synthesis of monodisperse nanocrystals, metal spinel nanoferrites MxFe3−xO4 (M = Fe, Mn, Zn) were prepared by the solvothermal method. Structural, morphological and magnetic characterisations were completed using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), energy-dispersive spectroscopy (EDS), atomic absorption spectroscopy (AAS), vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS) techniques. The size of the synthesised nanoferrites spanned from 7 to 16 nm based on TEM results. EDS, AAS and XPS evidenced successful doping of Zn2+ and Mn2+ into the Fe3O4 structure. XRD revealed the expansion of the cell unit of Fe3O4 with the substitution of the larger Zn2+ and Mn2+ ions. All prepared nanoferrites presented with superparamagnetism at room temperature (300 K) with a blocking temperature less than room temperature (TB

Syntheses and magnetic and structural characterization of hexa-iron complexes of derivatized salicylaldoximes are discussed. Complexation of Fe(BF4)2·6H2O with each ligand (H2L1 and H4L2) in a methanolic-pyridine solution resulted in hexa-iron compounds (C1 and C2, respectively), which each contain two near-parallel metal triangles of [Fe3–μ3-O], linked by six fluoride bridges and stabilized by a hydrogen-bonded proton between the μ3-O groups. Within each metal triangle of C2, Fe(III) ions are connected via the amine “straps” of (H4L2-2H). Variable-temperature magnetic susceptibility and Mössbauer data of C1 and C2 indicate the presence of dominant antiferromagnetic interactions between the high-spin (S = 5/2) Fe(III) centers. For C1, two quadrupole doublets are observed at room temperature and 5 K, consistent with structural data from which discrete but disordered [Fe3–μ3-O] and [Fe3–μ3-OH] species were inferred. For C2, a single sharp quadrupole doublet with splitting intermediate between those determined for C1 was observed, consistent with the symmetric [Fe3–μ3-O···H···μ3-O–Fe3] species inferred crystallographically from the very short μ3-O···μ3-O separation. The differences in the physical properties of the complexes, as seen in the Mössbauer, X-ray, and magnetic data, are attributed to the conformational flexibility imparted by the nature of the linkages between the closely related ligands.

Substituted [2.2]metaparacyclophanes are amongst the least studied of the simple cyclophanes. This is undoubtedly the result of the lengthy syntheses of these compounds. We report the simple synthesis of a rare example of a non-symmetric [2.2]metaparacyclophane. Treatment of [2.2]paracyclophane under standard nitration conditions gives a mixture of 4-nitro[2.2]paracyclophane, 4-hydroxy-5-nitro[2.2]metaparacyclophane and a cyclohexadienone cyclophane.

Ligands which incorporate second-sphere intramolecular hydrogen bonding show potential for enhancing selectivity and binding strength for beryllium. In this highlight review, recent advances in the...

9Be solution NMR spectroscopy is a useful tool for the characterisation of beryllium complexes. An updated comprehensive table of the 9Be NMR chemical shifts of beryllium complexes in solution is presented. The recent additions span a greater range of chemical shifts than those previously reported, and more overlap is observed between the chemical shift regions of four-coordinate complexes and those with lower coordination numbers. Four-coordinate beryllium species have smaller ω 1/2 values than the two- and three-coordinate species due to their higher order symmetry. In contrast to previous studies, no clear relationship is observed between chemical shift and the size and number of chelate rings.

The electrospray ionisation mass spectrometric (ESI-MS) behaviour of various complexes of beryllium have been investigated in the work described in this paper. These beryllium complexes were analysed in situ on a small scale by preparing appropriate molar mixtures of the Be2+ ion with ligands in a range of solvent systems. In view of the toxicity of beryllium compounds, this combinatorial type screening, involving miniscule amounts of material in solution, proved to be a safe strategy to pursue the coordination chemistry of beryllium. A variety of beryllium complexes were generated with various ligands in solutions and subjected to detailed characterisation by ESI-MS. These ligands, containing functional groups or architecture of interest, varied from simple ligands such as the acetate ion to more common beryllium chelators including hydroxy keto ligands (maltol, tropolone), malonic acid, chromotropic acid and citric acid. Generally, there was excellent correlation between the species observed in the mass spectrum and those confirmed to exist in solution by other techniques. This lent strong credence to the ESI-MS methodology used as an efficient analytical technique for the easy screening of a diverse range of potential ligands for the divalent beryllium ion.

Authors thank EaStCHEM and the School of Chemistry in St Andrews for support. OR thanks the Marsden Fund of the New Zealand Government (contract MAU1204), administered by the Royal Society of New Zealand for financial support of this work. Structures of aqueous [Be(H2O)4]2+, its outer-sphere and inner-sphere complexes with F-, Cl- and SO42-, as well as dinuclear complexes with a [Be(κ-OH)(κ-SO4)]+ core have been studied through Car-Parrinello molecular dynamics (CPMD) simulations with the BLYP functional. According to constrained CPMD/BLYP simulations and pointwise thermodynamic integration, the free energy of deprotonation of [Be(H2O)4]2+ and its binding free energy with F- are 9.6 kcal mol-1 and -6.2 kcal mol-1, respectively, in good accord with available experimental data. The computed activation barriers for replacing a water ligand in [Be(H2O)4]2+ with F- and SO42-, 10.9 kcal mol-1 and 13.6 kcal mol-1, respectively, are also in good qualitative agreement with available experimental data. These ligand substitution reactions are indicated to follow associative interchange mechanisms with backside (SN2-like) attack of the anion relative to the aquo ligand it is displacing. Outperforming static DFT computations of the salient kinetic and thermodynamic quantities involving simple polarizable continuum solvent models, CPMD simulations are validated as a promising tool to study structures and speciation of beryllium complexes in aqueous solution. Postprint

The speciation of beryllium chloride solutions has been investigated using electrospray ionization mass spectrometry in both positive and negative ion modes. The majority of observed species were m...

We report the synthesis and characterization of seven new tetranuclear 3d-4f complexes derived from the 3:3:1 reaction of 1,4-diformylnaphthalene-2,3-diol (H

Four tetranuclear heterobimetallic triangle complexes [L

We report the synthesis and crystal structure of the first quinolino[7,8

CuI complexes containing the bulky dialkylbiarylphosphane 2-(di-tert-butylphosphanyl)-2′,4′,6′-triisopropylbiphenyl ( t BuXPhos, L) and an ancillary ligand (Cl−, Br−, I−, MeCN, ClO4 − or SCN−) have been structurally characterized, namely, chlorido[2-(di-tert-butylphosphanyl)-2′,4′,6′-triisopropylbiphenyl-κP]copper(I), [CuCl(C29H45P)], 1, bromido[2-(di-tert-butylphosphanyl)-2′,4′,6′-triisopropylbiphenyl-κP]copper(I), [CuBr(C29H45P)], 2, [2-(di-tert-butylphosphanyl)-2′,4′,6′-triisopropylbiphenyl-κP]iodidocopper(I), [CuI(C29H45P)], 3, (acetonitrile-κN)[2-(di-tert-butylphosphanyl)-2′,4′,6′-triisopropylbiphenyl-κP]copper(I) hexafluoridophosphate, [Cu(CH3CN)(C29H45P)]PF6, 4, [2-(di-tert-butylphosphanyl)-2′,4′,6′-triisopropylbiphenyl-κP](perchlorato-κO)copper(I), [Cu(ClO4)(C29H45P)], 5, and di-μ-thiocyanato-κ2 S:N;κ2 N:S-bis{[2-(di-tert-butylphosphanyl)-2′,4′,6′-triisopropylbiphenyl-κP]copper(I)}, [Cu2(NCS)2(C29H45P)2], 6. Iodide complex 3 shows significant CuI–arene interactions, in contrast to its chloride 1 and bromide 2 counterparts, which is attributed to the weaker interaction between the iodide ion and the CuI centre. When replacing iodide with an acetonitrile (in 4) or perchlorate (in 5) ligand, the reduced interaction between the CuI atom and the ancillary ligand results in stronger CuI–arene interactions. No CuI–arene interactions are observed in dimer 6, due to the tricoordinated CuI centre having sufficient electron density from the coordinated ligands.

Catalysis is an important process across multiple disciplines, and there are still many challenges to be met. Enzymes, “nature’s catalysts”, display impressive efficacy with controlled selectivity and rapid throughput, so attempting to mimic these properties opens up exciting pathways in catalyst research. In recent years, metallo-organic coordination cages have shown promise in exploring these avenues. Their unique structures and modifiable properties present opportunities not available to traditional catalysts. This mini-review provides a general introduction to the field, then attempts to extract effects ascribed to interior versus surface or exterior influences, illustrating these with recently published results.

Electrospray ionization mass spectrometry (ESI MS) is a powerful technique for the study of coordination complexes because of its ability to analyze solution systems involving very low concentrations of metal complexes. In this work, the coordination chemistry of Be ions with a selection of well-known 1,3-diketone and related 1,2-diketone ligands has been investigated using ESI MS. With acetylacetone (Hacac), a range of acac-containing ions is observed, including [Be(acac)2H]+, [Be(acac)(MeOH) n]+ ( n = 1, 2), and polynuclear species such as the dinuclear [Be2(acac)3]+ and trinuclear [Be3O(acac)3]+. Density functional theory calculations indicate that the latter species has a central Be3(μ3-O) core, with each Be chelated (as opposed to being bridged) by an acac ligand. The effect of changing the substituents on 1,3-diketone was explored by an investigation of mixtures of Be2+ with other 1,3-diketones such as dibenzoylmethane (Hdbm), where the [Be(dbm)2H]+ ion showed a lesser tendency to undergo fragmentation and aggregation processes. Comparisons with the corresponding aluminum acetylacetone system were also made. In contrast, mixtures of Be2+ and the 1,2-diketones diacetyl and phenanthrenequinone showed poor metal-ligand interactions. Be2+ interacted with the 1,2-diketone benzil [PhC(O)C(O)Ph], forming the [Be(benzil) n]2+ ( n = 2-4) ions. The synthesis (from BeCl2) and X-ray structures of the dibenzoylmethanato (dbm) complex Be(dbm)2 and the benzil complex [BeCl2(benzil)] are also reported.

We report an improved method to make the ligand N,N′-(pyrazine-2,5-diylbis(methanylylidene))bis(2-(pyridin-2-yl)ethanamine) (L) and the subsequent complexation of this ligand to make the triangular metallo-macrocycles [Co3L3](ClO4)6·2H2O (C1·2H2O) and [Mn3L3](ClO4)6·3H2O (C2·3H2O). Single crystal X-ray analysis of both trimeric circular helicates reveal the complexes pack in enantiomeric pairs in close synergy with the accompanying anions.

Anion hydrolysis reactions between salicylaldoximato ligands (L '-L ''') and copper and iron BF4- metal salts, have resulted in the formation of new salicylaldoximato borate containing transition metal complexes: [Fe-2(L ' + 2H)(2)](BF4)(2)(MeOH)(4) (C1), [Fe-3(L '' + 4H)(OH)(2)(Py)(2)](BF4)(2)(H2O)(2)(Py)(2) (C2), and [Cu-2(L ''' + H)(2)Cl-2] (C3). Each of the complexes have been structurally characterised, revealing the indirect role boron plays in the formation of these complexes. For complexes C1 and C2, Mossbauer spectroscopy confirmed the existence of Fe(iii) oxidation states. SQUID magnetometry measurements were performed on complexes C2 and C3, revealing the presence of two competing exchange pathways between the three Fe(iii) centres in C2, with antiferromagnetic exchange dominating. For C3 weak antiferromagnetic exchange dominated between the two Cu(ii) centres.

Two series of tetradentate tripodal di-pyridine-based receptors designed to bind Be2+ cations have been studied in the aqueous phase at the B3LYP/6-311++G(d,p) computational level. The first series comprise simple tetrahedral receptors; the second series incorporates additional scaffolding groups capable of second sphere hydrogen-bonding in order to more finely tune the binding strength towards the Be2+ cation. Out of the five ligand candidates, one containing a tri-pyridyl N-donor along with a phenolato O-donor (L1) exhibited a significant improvement in binding energy stabilisation (47.8 kJ mol-1) towards the Be2+ cation in the presence of second-sphere H-bonding interactions.

We report the synthesis and characterization of four new tetranuclear Ni(ii) complexes, C1-C4, all of which exhibit defective dicubane cores. C1-C4 are derived from the same salicylaldoxime derived ligand, H2L1. Complexes C1 and C4 have isostructural cores, differing in structure only by solvate molecules. Magnetic and computational analyses have revealed that complexes C1, C2, and C4 exhibit competing ferro- and antiferromagnetic interactions, however the different solvated species in C1 and C4 leads to notably different magnitudes in their magnetic coupling constants. Theoretical magneto-structural studies show that the pairwise magnetic exchange interaction is highly dependent on the Ni-X-Ni angle, as revealed by orbital overlap calculations.

We report the synthesis and characterization of four new tetranuclear Ni(II) complexes, C1–C4, all of which exhibit defective dicubane cores. C1–C4 are derived from the same salicylaldoxime derived ligand, H2L1. Complexes C1 and C4 have isostructural cores, differing in structure only by solvate molecules. Magnetic and computational analyses have revealed that complexes C1, C2, and C4 exhibit competing ferro- and antiferromagnetic interactions, however the different solvated species in C1 and C4 leads to notably different magnitudes in their magnetic coupling constants. Theoretical magneto-structural studies show that the pairwise magnetic exchange interaction is highly dependent on the Ni–X–Ni angle, as revealed by orbital overlap calculations.

A comparative study between three experimentally known beryllium chelators (EDTA, NTP, and 10-HBQS) and two tetradentate tripodal di-pyridine-based receptors (HL and HL-NH

Quinolino[7,8

Quinolino[7, 8-h]quinoline is a superbasic compound, with a pKaH in acetonitrile greater than that of 1, 8-bis(dimethylaminonaphthalene) (DMAN), although its synthesis and the synthesis of its derivatives can be problematic. The use of halogen derivatives 4, 9-dichloroquinolino[7, 8-h]quinoline (16) and 4, 9-dibromoquinolino[7, 8-h]quinoline (17) as precursors has granted the formation of a range of substituted quinolinoquinolines. The basicity and other properties of quinolinoquinolines can be modified by the inclusion of suitable functionalities. The experimentally obtained pKaH values of quinolino[7, 8-h]quinoline derivatives show that N4, N4, N9, N9-tetraethylquinolino[7, 8- h]quinoline-4, 9-diamine (26) is more superbasic than quinolino[7, 8-h]quinoline. Computationally derived pKaH values of quinolinoquinolines functionalized with dimethylamino (NMe2), 1, 1, 3, 3- tetramethylguanidino (N=C(NMe2)2) or N, N, N′, N′, N ″, N″-hexamethylphosphorimidic triamido (N=P(NMe2)3) groups are significantly greater than those of quinolino[7, 8-h]quinoline. Overall, electron-donating functionalities are observed to increase the basicity of the quinolinoquinoline moiety, while the substitution of electron- withdrawing groups lowers the basicity.

A planar chiral secondary phosphine oxide based on [2.2]paracyclophane was synthesized and its chemistry investigated; it was shown to be a competent pre-ligand in palladium(0)-mediated reactions, and displayed promising activity in gold(I)-catalysed cyclisations. The secondary phosphine oxide could be transformed into a collection of P-stereogenic tertiary phosphine oxides. These are rare examples of the planar chirality of [2.2]paracyclophane being combined with a P-stereogenic centre. Unfortunately, epimerisation of the phosphorus stereocentre during reduction limits the use of this chemistry.

Beryllium has a unique combination of properties which has made it a vital component in a wide range of technical sectors and consumer industries. However, beryllium is extremely toxic and can cause chronic beryllium disease, for which there is no current cure. The toxicity of beryllium has limited the exploration of its chemistry, and as a result beryllium chemistry is underdeveloped in comparison to other alkaline earth metals. The development of selective chelating agents for beryllium has become paramount. Beryllium prefers tetrahedral coordination to ‘hard’ donor ligands and is most stable when coordinated in six-membered chelate rings. This review provides a description of reported ligands for beryllium and a comparison of their binding strengths with particular emphasis on donor ligands and binding modes and requirements for effective coordination of beryllium.

In this work we explored the relationship between the structure and solvent effects on the basicity of a large selection of conjugated N-heterocyclic nitrogen bases in different media: the polar aprotic solvent acetonitrile, the polar protic solvent water and the gas phase. Altogether, 58 previously unpublished basicity values in different media for 39 compounds are presented, including 30 experimentally determined pKa values in acetonitrile. We present the pKa and gas-phase basicity values for quino[7,8-h]quinoline, which is one of the most basic conjugated nitrogen heterocyclic compounds without basicity-enhancing substituents. The trends in basicity are rationalized by comparing the basicity data of related compounds in different solvents, as well as by using isodesmic reactions. The gas-phase basicity is predominantly determined by the ability of a molecule to disperse the excess positive charge over a large number of atoms. In solution the situation is less clear and smaller systems with localized charge often lead to higher basicities because of solvent effects. In particular, it was found that the fusion of an additional benzene ring does not always lead to an increase in basicity in solution: its effect can be either basicity-increasing or -decreasing, depending on the ring size, number and position of nitrogen atoms and medium. A correlation between the measured pKa values in MeCN and in water suggests that these two different solvents exert a similar effect on the basicity of the studied heterocycles.

In this study, we show that phosphate decreases the spore heat resistance by accelerating the rate of loss of cations from spores. Heat resistance of spores of Geobacillus stearothermophilus A1, D1, P3 and ATCC 12980 were determined in distilled water containing varying concentrations (0.1, 1 and 2% w/v) of di‑sodium phosphate. The average decimal reduction times (D value) for strains A1, D1, P3 and ATCC 12980 in distilled water were 5.8, 6.8, 5.7 and 9 min at 110 °C respectively. On the addition of 0.1, 1 and 2% w/v of di‑sodium phosphate, the average D110 values of all the strains in distilled water were lowered by 50, 61 and 70% respectively. Addition of 0.05% w/v of Na-EDTA to distilled water resulted in lowering of the average D110 value of all the strains by 55%. Heat resistance of spores of A1, D1, P3 and ATCC 12980 was found to be associated with the Dipicolinic Acid (DPA) content whose concentrations were 0.25, 0.30, 0.27 and 1.6 pg per spore respectively. Analysis by atomic absorption spectroscopy revealed that the phosphate present in the heating medium causes excess release of calcium from spores with 2% w/v phosphate being highly effective, thus confirming the chelating effect of phosphate. This study provides insight into the heat resistance and the increased heat sensitivity of spores of G. stearothermophilus A1, D1 and P3 in the presence of phosphate, which can be used in the design of Cleaning in Place (CIP) systems involving phosphate based cleaning agents to combat biofilms and spores in the dairy industry.

In this study we compared a heat resistance of spores of Geobacillus stearothermophilus A1, D1, P3 and ATCC 12980 obtained using a milk biofilm system under continuous flow with previously reported values obtained by a sporulating medium. The average decimal reduction times of A1, D1, P3 and ATCC 12980 were 4.2, 4.9, 4.1 and 7.9 min, respectively, and were not significantly different (p

Tribenzylphosphane sulfide (SPBn3) reacts with [Cu(CH3CN)4]PF6 in a 2:1 ratio to give [Cu(CH3CN)(SPBn3)2]PF6 whereas with [Ag(CH3CN)4]PF6 in the same ratio it forms [Ag2(SPBn3)3](PF6)2. The crystal structure of the Cu(I) complex shows it to contain discrete 3-coordinate [Cu(CH3CN)(SPBn3)2]+ cations and [PF6]− anions with the Cu atom lying in the plane formed by the two coordinated sulfur atoms and the nitrogen from the coordinated acetonitrile molecule. The Ag complex is a dinuclear species with the one silver atom being 3-coordinate and the other 4-coordinate. Each of the SPBn3 molecules forms a Ag–C η1-bond with one of the aromatic rings thus blocking the coordination of further SPBn3 ligands. The two Ag centers are linked by a bridging sulfur and a weaker interaction with carbon from the aromatic ring of the same tribenzylphosphane sulfide.

In this paper, we present our findings on a series of copper(ii) 2,2′-bipyridyl (bipy) complexes that inhibit the oxidation of thiosulfate, a current problem in the gold leaching process. The formation of six complexes, five of which have been structurally characterized by X-ray crystallography, illustrate a thermally induced, controllable switching between oxidation states, which in turn inhibits the oxidation of thiosulfate. These findings give further insight and understanding into the rich chemistry of the coinage metals and the hydrolytic processes involved with gold leaching.

Trimellitic anhydride chloride was used to generate a water soluble amphoteric chitosan derivative (CTAA). CTAA was combined with alginate to facilitate direct targeting of 5-FU to the colon. The structure of CTAA was characterized by FTIR, 1 H/ 13 C NMR and HSQC. The physical properties of the CTAA hydrogel were analyzed by scanning electron microscopy, X-ray diffraction and thermogravimetry. Inhibition of a pancreatic enzyme's activity and cytotoxicity studies of CTAA were also carried out. Sodium alginate was mixed with CTAA to form a polyelectrolyte complex film and resulted in improved controlled drug release. Swelling characteristics of the films as a function of pH were also investigated. An optimized formulation was exposed to conditions simulating the stomach, small intestine, and colon. The CTAA/alginate formulation used in this preliminary study presents potential for at least 28% of ingested 5-FU to arrive at the colon ready for release by colonic enzymes. Films were chosen in the study to severely stretch the capabilities of the CTAA/alginate system. The system nevertheless will need modifying for in vivo delivery to the colon.

© 2017 The Royal Society of Chemistry. The synthesis of three planar chiral pseudo-gem disubstituted [2.2]paracyclophane-derived P,N-pre-ligands is reported along with preliminary results of their activity in the amination of aryl bromides and chlorides. The pseudo-gem aminophosphines were capable of mediating the coupling reaction at a loading of 1 mol%.

This study has developed a new generation of crosslinked chitosan-based films using symmetric aromatic dianhydrides as crosslinking agents. The formation of the dianhydride-crosslinked chitosan hydrogel films was confirmed using Fourier transform infrared and solid-state 13C NMR spectral analyses. The films obtained from these derivatives were characterized by their thermal, swelling and hydrophilic properties. The results showed that introducing a cyclic imide moiety into the chitosan matrices played a significant role in enhancing the thermal properties of these chitosan films. It was found that even at high levels of substitution, thermal stability of the studied chitosan derivatives was improved, in spite of a reduction in crystallinity. Heterocyclic imide linkages produced networks that were insoluble in both acidic and alkaline media but allowed swelling in aqueous media. An increase in the hydrophobicity of the chitosan film surfaces was observed after introduction of the cyclic imide moiety. These engineered films produced noteworthy results concerning their thermal and swelling properties. There is a need to further investigate these films for drug delivery and biomaterials applications. © 2014 Society of Chemical Industry

We report the synthesis, crystal structures and ESR measurements of two new copper(II) complexes having the general formula [Cu(1)(CH3CN)3](ClO4)2 involving the ligands 4,9-dichloroquino[7,8-h]quinoline 1a and quino[7,8-h]quinoline 1b.

In this communication we report the short synthesis of a variety of planar chiral triazole-based phosphanes. These molecules have been readily prepared from 4-azido[2.2]paracyclophane in two steps. It was observed that the stability of the resulting phosphanes was dependent on the C-4 substituent. The efficacy of the new phosphanes in the palladium-mediated Suzuki–Miyaura coupling reaction was evaluated. The phosphanes proved to be more effective than previously prepared planar chiral [2.2]paracyclophane-based phosphanes.

A new route to unsymmetrical derivatives of quino[7,8-h]quinoline was developed. Substitutions at the 2,11-, 4,9- and 6,7-positions of quino[7,8-h]quinoline were also successfully performed. X-ray crystal structure determinations of the resulting products revealed the propensity for derivatives of this molecule to exist in either stabilised keto or imino forms as a result of the formation of a strong intramolecular N–H···N hydrogen bond.