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Crystal structures described as concomitant triclinic (I) and monoclinic (II) polymorphs of meso-(E,E)-1,1′-[1,2-bis(4-chlorophenyl)ethane-1,2-diyl]bis(phenyldiazene) [Mohamed et al. (2016). Acta Cryst. C72, 57–62] have been re-investigated. The published model for II was distorted due to forcing the symmetry of space group C2/c on an incomplete structure model. It is shown here to be a likely three-component superposition of S,S and R,R enantiomers with a lesser amount of the meso form. A detailed analysis of how the improbable distortion in the published model aroused suspicion and the subsequent construction of undistorted chemically and crystallographically plausible alternatives having the symmetry of Cc and C2/c is presented. For the sake of completeness, an improved model for the triclinic P-1 structure of the meso isomer I, revised to include a minor disorder component, is also given.

Cyclic porphyrin oligomers have been studied as models for photosynthetic light-harvesting antenna complexes and as potential receptors for supramolecular chemistry. Here, we report the synthesis of unprecedented β,β-directly linked cyclic zinc porphyrin oligomers, the trimer (CP3) and tetramer (CP4), by Yamamoto coupling of a 2,3-dibromoporphyrin precursor. Their three-dimensional structures were confirmed by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and single-crystal X-ray diffraction analyses. The minimum-energy geometries of CP3 and CP4 have propeller and saddle shapes, respectively, as calculated using density functional theory. Their different geometries result in distinct photophysical and electrochemical properties. The smaller dihedral angles between the porphyrin units in CP3, compared with CP4, result in stronger π-conjugation, splitting the ultraviolet–vis absorption bands and shifting them to longer wavelengths. Analysis of the crystallographic bond lengths indicates that the central benzene ring of the CP3 is partially aromatic [harmonic oscillator model of aromaticity (HOMA) 0.52], whereas the central cyclooctatetraene ring of the CP4 is non-aromatic (HOMA –0.02). The saddle-shaped structure of CP4 makes it a ditopic receptor for fullerenes, with affinity constants of (1.1 ± 0.4) × 105 M–1 for C70 and (2.2 ± 0.1) × 104 M–1 for C60, respectively, in toluene solution at 298 K. The formation of a 1:2 complex with C60 is confirmed by NMR titration and single-crystal X-ray diffraction.

Six disubstituted ligands based upon 2-(2′-pyridinyl/pyrazinyl)quinoline-4-carboxylic acids have been synthesised, solvent-free, in one step from a range of commercially available isatin derivatives. These species behave as ancillary chelating ligands for Ir(III) complexes of the form [Ir(C^N)2(N^N)]PF6 (where C^N=cyclometalating ligand; N^N=2-(2′-pyridinyl/pyrazinyl)quinoline-4-carboxylic acids). An X-ray crystallographic study on one complex shows a distorted octahedral geometry wherein a cis-C,C and trans-N,N coordination mode is observed for the cyclometalating ligands. DFT calculations predicted that variations in N^N ligand from 2,2′-bipyridine to L1–6 should localise the LUMO on to the Ln ligand and that the complexes are predicted to display MLCT/LLCT character. All complexes displayed luminescence in the deep red part of the visible region (674–679 nm) and emit from triplet states, but with little apparent tuning as a function of L1–6. Further time-resolved transient absorption spectroscopy supports the participation of these triplet states to the excited state character.

The synthesis and characterization of six new substituted guanidium tetrahydroxidohexaoxidopentaborate(1-) salts are reported: [C(NH2)2(NHMe)][B5O6(OH)4]·H2O (1), [C(NH2)2(NH{NH2})][B5O6(OH)4] (2), [C(NH2)2(NMe2)][B5O6(OH)4] (3), [C(NH2)(NMe2)2][B5O6(OH)4] (4), [C(NHMe)(NMe2)2][B5O6(OH)4]·B(OH)3 (5), and [TBDH][B5O6(OH)4] (6) (TBD = 1,5,7-triazabicyclo [4.4.0]dec-5-ene). Compounds 1–6 were prepared as crystalline salts from basic aqueous solution via self-assembly processes from B(OH)3 and the appropriate substituted cation. Compounds 1–6 were characterized by spectroscopic (NMR and IR) and by single-crystal XRD studies. A thermal (TGA) analysis on compounds 1–3 and 6 demonstrated that they thermally decomposed via a multistage process to B2O3 at >650 °C. The low temperature stage (2O. Reactant stoichiometry, solid-state packing, and H-bonding interactions are all important in assembling these structures. An analysis of H-bonding motifs in known unsubstituted guanidinium salts [C(NH2)3]2[B4O5(OH)4]·2H2O, [C(NH2)3][B5O6(OH)4]·H2O, and [C(NH2)3]3[B9O12(OH)6] and in compounds 1–6 revealed that two important H-bonding R22(8) motifs competed to stabilize the observed structures. The guanidinium cation formed charge-assisted pincer cation–anion H-bonded rings as a major motif in [C(NH2)3]2[B4O5(OH)4]·2H2O and [C(NH2)3]3[B9O12(OH)6], whereas the anion–anion ring motif was dominant in [C(NH2)3][B5O6(OH)4]·H2O and in compounds 1–6. This behaviour was consistent with the stoichiometry of the salt and packing effects also strongly influencing their solid-state structures.

Structurally defined graphene nanoribbons (GNRs) have emerged as promising candidates for nanoelectronic devices. Low bandgap (< 1 eV) GNRs are particularly important when considering the Schottky barrier in device performance. Here, we demonstrate the first solution synthesis of 8-AGNRs through a carefully designed arylated polynaphthalene precursor. The efficiency of the oxidative cyclode-hydrogenation of the tailor-made polymer precursor into 8-AGNRs was validated by FT-IR, Raman, and UV-vis-near-infrared (NIR) absorption spectroscopy, and further supported by the synthesis of naphtho[1,2,3,4-ghi]perylene derivatives (1 and 2) as subunits of 8-AGNR, with a width of 0.86 nm as suggested by the X-ray single crystal analysis. The resulting 8-AGNR exhibited a remarkable NIR absorption extending up to ~2400 nm, corresponding to an optical bandgap as low as ~0.52 eV. Moreover, optical-pump TeraHertz-probe spectroscopy revealed a charge-carrier mobility in the dc limit of ∼270 cm2 V–1 s–1 for the 8-AGNR

Treatment of a κ1-P-monodentate bicyclic diphosphane iridium(iii) complex with a labile gold(i) precursor afforded an unusual IrIII/AuI complex in which the P-P single bond has been cleaved. This reaction was cleanly reversed upon addition of tertiary phosphine. Carbon-carbon bond activation, across neighbouring P2C2N rings of the coordinated bicyclic diphosphane, occurred upon thermolysis of the IrIII/AuI complex.

The solid-state behaviour of five ionophore-encapsulated TCNQ complexes: (18-crown-6)K(TCNQ)2.5 (1), ([2.2.2]-cryptand)K(TCNQ)2.5 (2), (benzo-18-crown-6)K(TCNQ)2 (3), (dibenzo-18-crown-6)K(TCNQ)2 (4), and (dicyclohexano-18-crown-6)K(TCNQ)3 (5) has been explored. For both 1 and 2, the TCNQ components assemble as a pentameric repeat unit within infinite TCNQ columns with the cation complex sitting in a cavity between the columns; whereas for 3 and 4, neighbouring (crown ether)K+ complexes form dimers involving K+–π interactions which further assemble into one-dimensional columns sitting between infinite TCNQ stacks. In the solid-state complex 5, the crown ether adopts a chair conformation with the resulting (crown ether)K+ complex assembling into a one-dimensional ladder. Pairs of TCNQ dimers separated by an isolated TCNQ unit form infinite TCNQ columns. IR and Raman spectroscopy reveal the presence of partially charged TCNQ units within all five TCNQ complexes (1–5) and resistivity studies indicate that all five TCNQ complexes (1–5) are more conductive than the corresponding simple KTCNQ salts. Preliminary EPR studies of 1 and 2 indicate typical behaviour of complex TCNQ salts (containing both TCNQ0 and TCNQ˙−).

During the racemization of a novel pharmaceutical spirocyclic imidazole–amine compound, namely, 6′-bromo-N-(6′-bromo-4-methoxy-4′′-methyl-3′H-dispiro[cyclohexane-1,2′-indene-1′,2′′-imidazol]-5′′-yl)-4-methoxy-4′′-methyl-3′H-dispiro[cyclohexane-1,2′-indene-1′,2′′-imidazol]-5′′-imine, C36H41Br2N5O2, two impurities were isolated. These impurities were clearly dimers from mass spectroscopic analysis, however single-crystal diffraction characterization was required for the assignment of stereochemistry. The single-crystal diffraction results revealed subtly different structures to those proposed, due to an unexpected proton transfer. The dimers contain four stereocentres, but two of primary interest, and are centrosymmetric, so after careful structure refinement and close inspection it was possible to unambiguously assign the stereochemistry of both the homochiral [(S),(S)- and (R),(R)-] and the heterochiral [(S),(R)- and (R),(S)-] compounds.

A series of 2-phenylquinoxaline ligands have been synthesised that introduce either CF3 or OCF3 electron-withdrawing groups at different positions of the phenyl ring. These ligands were investigated as cyclometalating reagents for platinum(II) to give neutral complexes of the form [Pt(C^N)(acac)] (in which C^N=cyclometalating ligand; acac=acetyl acetonate). X-ray crystallographic studies on three examples showed that the complexes adopt an approximate square planar geometry. All examples revealed strong Pt−Pt linear contacts of 3.2041(6), 3.2199(3) and 3.2586(2) Å. The highly coloured complexes display efficient visible absorption at 400–500 nm (ϵ ≈5000 M−1 cm−1) and orange red photoluminescent characteristics (λem=603–620 nm; Φem ≤37 %), which were subtly tuned by the ligand. Triplet emitting character was confirmed by microsecond luminescence lifetimes and the photogeneration of singlet oxygen with quantum efficiencies up to 57 %. Each complex was investigated as a photosensitiser for triplet–triplet annihilation energy upconversion using 9,10-diphenylanthracene as the annihilator species: a range of good upconversion efficiencies (ΦUC 5.9–14.1 %) were observed and shown to be strongly influenced by the ligand structure in each case.

The synthesis of two thiosemicarbazone derivatised ligands (L1 and L2) was accomplished via the reaction of 1-(2-pyridinyl)ethanone hydrazone and either benzoyl or pivaloyl isothiocyanate. A range of Ni(II), Cu(II) and Zn(II) mononuclear complexes of these thiosemicarbazone ligands have been synthesized providing insight on the reactivity of the ligands. These complexes (1–12) have been characterized by high resolution mass spectrometry, IR, UV–vis., 1H and 13C NMR spectroscopies, elemental analysis and magnetic measurements. The solid-state molecular structures of eight examples were successfully determined by single crystal X-ray diffraction.

The syntheses of the 4,4′-trimethylenebis(N-methylpiperidine):boric acid (1:1) co-crystal, 4,4′-(1-MeNC5H9)2(CH2)3.B(OH)3 (1), and a zwitterionic tetrahydroxidohexaoxidopentaboron adduct, [B5O6(OH)4(κN-NH2CH2CH2NHEt2).H2O (2), (NH2CH2CH2NEt2 = deen) from appropriate combinatorial libraries primed with B(OH)3, are reported together with their spectroscopic (NMR, IR) and single-crystal XRD characterization data. Solid-state H-bond interactions are the likely strong drivers for their formation, and these are described in detail. H-bond networks present in co-crystal 1 include C22(16), R22(8), and R66(36) whilst zwitterionic pentaboron derivative 2 has three R22(8) intermolecular H-bond interactions and the Et2NH- group is involved in a S(7) intramolecular H-bond. Thermal (TGA/DSC) data are also reported for 1 which thermally decomposes to B2O3, in a multistage process: dehydration (60–70 °C) and oxidation and further dehydration (90–700 °C).

The direct synthesis of 1,1′,2,2′-tetralithioferrocene from1,1,2,2tetrabromoferrocene is reported. In addition, the related 1,1′,2,2′,3,3′-hexalithioferrocene is also described, prepared directly from 1,1′,2,2′,3,3′-hexabromoferrocene. These lithioferrocenes may be isolated as orange red (tetralithio) and red (hexalithio) powders, respectively. When these are prepared in situ and reacted with chlorotrimethylsilane, the corresponding 1,1′,2,2-tetrakis(trimethylsilyl)ferrocene and 1,1′,2,2′,3,3′′-hexakis(trimethylsilyl)ferrocene are obtained as red and crimson crystalline solids, respectively. The single-crystal structures of 1,1′,2,2′-tetrakis(trimethylsilyl)ferrocene (11) and 1,1′,2,2,3,3′-hexakis(trimethylsilyl)ferrocene (12) have been determined and are described.

Molecular self-assembly is the spontaneous association of simple molecules into larger and ordered structures 1. It is the basis of several natural processes, such as the formation of colloids, crystals, proteins, viruses and double-helical DNA 2. Molecular self-assembly has inspired strategies for the rational design of materials with specific chemical and physical properties 3, and is one of the most important concepts in supramolecular chemistry. Although molecular self-assembly has been extensively investigated, understanding the rules governing this phenomenon remains challenging. Here we report on a simple hydrochloride salt of fampridine that crystallizes as four different structures, two of which adopt unusual self-assemblies consisting of polyhedral clusters of chloride and pyridinium ions. These two structures represent Frank–Kasper (FK) phases of a small and rigid organic molecule. Although discovered in metal alloys 4,5 more than 60 years ago, FK phases have recently been observed in several classes of supramolecular soft matter 6–11 and in gold nanocrystal superlattices 12 and remain the object of recent discoveries 13. In these systems, atoms or spherical assemblies of molecules are packed to form polyhedra with coordination numbers 12, 14, 15 or 16. The two FK structures reported here crystallize from a dense liquid phase and show a complexity that is generally not observed in small rigid organic molecules. Investigation of the precursor dense liquid phase by cryogenic electron microscopy reveals the presence of spherical aggregates with sizes ranging between 1.5 and 4.6 nanometres. These structures, together with the experimental procedure used for their preparation, invite interesting speculation about their formation and open different perspectives for the design of organic crystalline materials.

The reaction between differently substituted borasiloxanes and 2,5-bis(3-pyridylethynyl)thiophene provided the first example of luminescent borasiloxane-based chiral helices held together by N-B bonds. The starting building blocks and the helices were fully characterized, and the nature of the N-B bond rationalized by means of theoretical calculations.

An investigation of the solid-state behaviour of five 12-crown-4 alkali metal TCNQ complexes, (12-crown-4)2LiTCNQ (1), (12-crown-4)2NaTCNQ (2), (12-crown-4)2Li(TCNQ)2 (3), (12-crown-4)2Na(TCNQ)2 (4), and (12-crown-4)2K(TCNQ)2 (5), reveals an unusual “cross-stitch” packing motif with the extended face-to-face π-stacked TCNQ˙− columns present in complexes 1 and 2. The effect of the presence of additional neutral TCNQ0 has also been explored.

The self-assembly and self-organization of water molecules are relevant in many fields of research. When water spontaneously reacts with 2,2,6,6-tetramethylpiperidine (TMP) to form colourless and crystalline discrete needles, only in the exact ratio of 2:1, it is important to understand the phenomenon. Single-crystal X-ray and neutron diffraction data have unveiled that TMP self-assembles around columns of water molecules, and as such, the resulting adduct may be described as a series of molecular water pipes.

Bis-terdentate (N^N^N) ligands coordinated to Cr(III) yield complexes that display near-IR emission under aerated solvent conditions at room temperature.\ud \ud Graphical abstract: Long-lived, near-IR emission from Cr(iii) under ambient conditions\ud Cr(iii) complexes have attracted interest due to their optical,1 (photo)redox and magnetic properties.2 Cr(iii) photoluminescence,3 from a discreet coordination complex was first reported in the 1960s.4 The photophysics of Cr(iii) complexes is generally dominated by metal-centred excited states.5–7 A strong, pseudo-octahedral ligand field at Cr(iii) yields the possibility for populating doublet excited states (2E and 2T), while simultaneously preventing 4T2/2E back intersystem crossing. As relaxation from these excited states to the 4A2 ground state is spin forbidden, long-lived phosphorescence can be observed. However, Cr(iii) species are often hampered by poor emissivity. Deoxygenated, deuterated solvents and deuteriation of ligands has been employed to help minimise quenching from non-radiative multiphonon relaxation pathways.8\ud \ud In contrast to well-known precious metal lumophores, earth-abundant Cr(iii) complexes of archetypal diimine ligands typically show Cr-centred phosphorescence in the 650–760 nm range. Related heteroleptic complexes provide some rational tuning of emission within similar wavelength ranges.9\ud \ud Scheme 1 describes some important luminescent Cr(iii) complexes, most of which have been reported in the last few years. Consideration of the N–Cr–N bite angles of the coordinated ligands is key. Thus, larger six-membered chelate rings are well suited in optimizing N–Cr–N bite angles towards 90° and this in turn reduces non-radiative deactivation.7 Recent studies have clearly demonstrated the use of ligands such as N,N′-dimethyl-N-N′-dipyridine-2-yl-pyridine-2,6-diamine (ddpd),10 2,6-bis(2-pyridylmethyl)pyridine (bpmp),11 and 1,1,1-tris(pyrid-2-yl)ethane (tpe)12 that yield Cr(iii) complexes with more intense emission properties and longer lifetimes.

The synthesis of six N,N′-substituted thiourea ligands (L1a–L3b) was achieved in two steps. A corresponding extensive series of Cu(I), Cu(II), Ni(II) and Zn(II) complexes (1–24) with varying formulations were synthesised from these ligands by the reaction of a 1 : 1 or a 1 : 2 mixture of Cu(II), Ni(II) and Zn(II) perchlorate or chloride salts. Complexes 1–24 have been comprehensively characterised by mass spectrometry, elemental analysis, UV-vis., IR, and 1H and 13C{1H} NMR spectroscopies where applicable. The X-ray crystal structures were obtained for eight examples: [(L1a)2Cu]ClO4 (1), [(L1c)2Zn](ClO4)2 (4), [(L2a)2Cu]ClO4 (6), [(L2c)2Ni](ClO4)2 (7), [(L1b)2Cu](ClO4) (15), [(L1b)CuCl] (16), [(L4)2CuCl2] (19) and [(L3b)CuClO4] (21). These studies reveal that L1c and L2c represent ligands that have undergone cleavage during reaction with the metal salt; L4 represents an intramolecular rearrangement (via a Hugershoff reaction) of L2b; and in most cases Cu(II) is reduced to Cu(I) during the ligand reaction. The X-ray crystal structures also reveal that 1, 4, 6, 15 and 16 are monometallic species in the solid state; that Cu(I) in 1, 6, 15 and 16 and Zn(II) in 4 are arranged in a distorted tetrahedral geometry; that Cu(I) in 21 adopts a trigonal planar geometry; and that in 7 and 19 the Ni(II) and Cu(II) centres, respectively, possess square planar geometry. Preliminary studies on the biological activity (using the Malaria Sybr Green I Fluorescence assay) of the thiourea containing complexes suggests that the d10 complexes, and increased ligand stoichiometries, may afford higher potency.

Two ligands based upon a 2,6-disubstituted pyridine bridge introduce bis-quinoxalinyl units in a fashion that yields analogues to the archetypal terdentate ligand, 2,2′:6′,2′′-terpyridine. The ligands were synthesised from the key intermediate 2,6-bis(bromoacetyl)pyridine: a new, high-yielding route is described for this reagent. Two ligand variants (differentiated by H/Me substituents on the quinoxaline ring) were explored as coordinating moieties for iridium(III) in the development of luminescent complexes. Computational studies (DFT approaches employing B3LYP, B3LYP/LANL2DZ, and M062X/LANL2DZ levels) were used to investigate the geometric and coordination mode preferences of the new ligands and two possibilities arose from theoretical investigations: [Ir(N^N^N)2]3+ and [Ir(N^N^C)2]+, with the former predicted to be more energetically favourable. Upon synthesis and isolation of the Ir(III) complexes, X-ray crystallographic studies revealed coordination spheres that were cyclometalated, the structures both showing a [Ir(N^N^C)2]PF6 arrangement. Further spectroscopic characterization via NMR confirmed the ligand arrangements in the complexes, and photophysical studies, supported by DFT, showed that a mixture of metal-to-ligand charge transfer (MLCT) and intra-ligand charge transfer (ILCT) character is likely to contribute to the emission features of the complexes, which phosphoresce orange-red (λem = 580–618 nm). The emission wavelength was influenced by the substituents on the quinoxaline ring (H vs. Me), thereby implying further tuneability is possible with future ligand iterations.

Porous Liquids (PLs) are a new class of material that possess both fluidity and permanent porosity. As such they can act as enhanced, selective solvents and may ultimately find applications which are not possible for porous solids, such as continuous flow separation processes. Type II PLs consist of empty molecular hosts dissolved in size-excluded solvents and to date have mainly been based on hosts that have limited chemical and thermal stability. Here we identify Noria, a rigid cyclic oligomer as a new host for the synthesis of more robust Type II PLs. Although the structure of Noria is well-documented, we find that literature has overlooked the true composition of bulk Noria samples. We find that bulk samples typically consist of Noria (ca. 40%), a Noria isomer, specifically a resorcinarene trimer, “R3” (ca. 30%) and other unidentified oligomers (ca. 30%). Noria has been characterised crystallographically as a diethyl ether solvate and its 1H NMR spectrum fully assigned for the first time. The previously postulated but unreported R3 has also been characterised crystallographically as a dimethyl sulfoxide solvate, which confirms its alternative connectivity to Noria. Noria and R3 have low solubility which precludes their use in Type II PLs, however, the partially ethylated derivative Noria-OEt dissolves in the size-excluded solvent 15-crown-5 to give a new Type II PL. This PL exhibits enhanced uptake of methane (CH4) gas supporting the presence of empty pores in the liquid. Detailed molecular dynamics simulations support the existence of pores in the liquid and show that occupation of the pores by CH4 is favoured. Overall, this work revises the general accepted composition of bulk Noria samples and shows that Noria derivatives are appropriate for the synthesis of more robust Type II PLs., Porous Liquids (PLs) are a new class of material that possess both fluidity and permanent porosity. Here we identify Noria, a rigid cyclic oligomer as a new host for the synthesis of more robust Type II PLs.

A series of ligands have been synthesized based upon a polysubstituted 2-phenylquinoxaline core structure. These ligands introduce different combinations of fluorine and methyl substituents on both the phenyl and quinoxaline constituent rings. The resultant investigation of these species as cyclometalating agents for Ir(III) gave cationic complexes of the form [Ir(C^N)2(bipy)]PF6 (where C^N = cyclometalating ligand; bipy = 2,2′-bipyridine). X-ray crystallographic studies were conducted on four complexes and each revealed the expected distorted octahedral geometry based upon a cis-C,C and trans-N,N ligand arrangement at Ir(III). Supporting computational studies predict that each of the complexes share the same general descriptions for the frontier orbitals. TD-DFT calculations suggest MLCT contributions to the lowest energy absorption and a likely MLCT/ILCT/LLCT nature to the emitting state. Experimentally, the complexes display tunable luminescence across the yellow-orange-red part of the visible spectrum (λem = 579–655 nm).

We report the synthesis, magnetic and conducting properties of a new manganese complex [MnII(hfac)2(IMHPhOPh)]2[MnII(hfac)3](IMH2PhOPh) (1), containing the reduced forms (IMHPhOPh and IMH2PhOPh) of the NIT-PhOPh radical (NIT-PhOPh = 2,4‘-benzoxo-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide). Direct current magnetic susceptibility studies revealed the presence of weak antiferromagnetic exchange interactions between the metal ions, within the [MnII(hfac)2(IMHPhOPh)]2 unit. The EPR spectra of 1 exhibit simultaneous contributions of both the monomeric [MnII(hfac)3] and dimeric [MnII(hfac)2(IMHPhOPh)]2 species. Conductivity measurements shown that the electrical conduction of 1 is dominated by Ohm’s law, with a conductance value of 1.3 (6) × 10−9 S/cm.

Several oxidoborates, self-assembled from B(OH)3 and templated by cationic Ni(II) coordination compounds, were synthesized by crystallization from aqueous solution. These include the ionic compounds trans-[Ni(NH3)4(H2O)2][B4O5(OH)4].H2O (1), s-[Ni(dien)2][B5O6(OH)4]2 (dien = N-(2-aminoethyl)-1,2-ethanediamine (2), trans-[Ni(dmen)2(H2O)2] [B5O6(OH)4]2.2H2O (dmen = N,N-dimethyl-1,2-diaminoethane) (3), [Ni(HEen)2][B5O6(OH)4]2 (HEen = N-(2-hydroxyethyl)-1,2-diaminoethane) (4), [Ni(AEN)][B5O6(OH)4].H2O (AEN = 1-(3-azapropyl) -2,4-dimethyl-1,5,8-triazaocta-2,4-dienato(1-)) (5), trans-[Ni(dach)2(H2O)2][Ni(dach)2] [B7O9(OH)5]2.4H2O (dach = 1,2-diaminocyclohexane) (6), and the neutral species trans-[Ni(en)(H2O)2{B6O7(OH)6}].H2O (7) (en = 1,2-diaminoethane), and [Ni(dmen)(H2O){B6O7(OH)6}].5H2O (8). Compounds 1–8 were characterized by single-crystal XRD studies and by IR spectroscopy and 2, 4–7 were also characterized by thermal (TGA/DSC) methods and powder XDR studies. The solid-state structures of all compounds show extensive stabilizing H-bond interactions, important for their formation, and also display a range of gross structural features: 1 has an insular tetraborate(2-) anion, 2–5 have insular pentaborate(1-) anions, 6 has an insular heptaborate(2-) anion (‘O+’ isomer), whilst 7 and 8 have hexaborate(2-) anions directly coordinated to their Ni(II) centers, as bidentate or tridentate ligands, respectively. The Ni(II) centers are either octahedral (1–4, 7, 8) or square-planar (5), and compound 6 has both octahedral and square-planar metal geometries present within the structure as a double salt. Magnetic susceptibility measurements were undertaken on all compounds.

A series of heteroleptic, neutral iridium(III) complexes of the form [Ir(L)2(N^O)] (where L = cyclometalated 2,3-disubstituted quinoxaline and N^O = ancillary picolinate or pyrazinoate) are described in terms of their synthesis and spectroscopic properties, with supporting computational analyses providing additional insight into the electronic properties. The 10 [Ir(L)2(N^O)] complexes were characterized using a range of analytical techniques (including 1H, 13C, and 19F NMR and IR spectroscopies and mass spectrometry). One of the examples was structurally characterized using X-ray diffraction. The redox properties were determined using cyclic voltammetry, and the electronic properties were investigated using UV–vis, time-resolved luminescence, and transient absorption spectroscopies. The complexes are phosphorescent in the red region of the visible spectrum (λem = 633–680 nm), with lifetimes typically of hundreds of nanoseconds and quantum yields ca. 5% in aerated chloroform. A combination of spectroscopic and computational analyses suggests that the long-wavelength absorption and emission properties of these complexes are strongly characterized by a combination of spin-forbidden metal-to-ligand charge-transfer and quinoxaline-centered transitions. The emission wavelength in these complexes can thus be controlled in two ways: first, substitution of the cyclometalating quinoxaline ligand can perturb both the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital levels (LUMO, Cl atoms on the ligand induce the largest bathochromic shift), and second, the choice of the ancillary ligand can influence the HOMO energy (pyrazinoate stabilizes the HOMO, inducing hypsochromic shifts)., Heteroleptic neutral iridium(III) complexes [Ir(L)2(N^O)] (where N^O = picolinate or pyrazinoate) that incorporate cyclometalated quinoxaline ligands demonstrate tunable emission in the red region of the visible spectrum.

The pentaborate(1-) salt, [Cu(dmen)2(H2O)2][B5O6(OH)4]2.2B(OH)3(dmen = N,N′-dimethylethylenediamine, MeHNCH2CH2NHMe), has been synthesized in 48% yield as a crystalline product by reaction ...

The synthesis and characterization of a C2 (ethane) linked bis(trimethylammonium) pentaborate salt, [Me3NCH2CH2NMe3][B5O6(OH)4]2 (1), is reported. Compound 1 has been characterized by 1H, 11B, and 13C NMR Spectroscopy, IR spectroscopy, thermal (TGA/DSC) analysis, and single-crystal X-ray diffraction. There are two independent crystallographic pentaborate(1-) anions in the solid-state structure and these link by H-bonds at β-sites into a centrosymmetric tetrameric chain. These chains are crossed-linked by R22(8) H-bond motifs to α-sites of neighboring pentaborate tetrameric units. The [Me3NCH2CH2NMe3]2+ cations are located between these tetrameric pentaborate(1-) units.

Two novel salts containing the anion [Ni(mnt)2]− (mnt = maleonitriledithiolate) have been synthesized. The counter-ions, [Fe(II)(L1 or L2)2], are cationic complexes where L1 and L2 are methylated derivatives of 2,6-bis(pyazolyl)pyridine or pyrazine, which are similar to ligands found in a series of spin-crossover (SCO) complexes. Both salts are characterized by variable temperature single crystal X-ray diffraction and bulk magnetization measurements. Compound 1, [Fe(II)(L1)2][Ni(mnt)2]2 displays an incomplete and gradual SCO up to 300 K, followed by a more rapid increase in the high-spin fraction between 300 and 350 K. Compound 2, [Fe(II)(L2)2][Ni(mnt)2]2.MeNO2, shows a gradual, but more complete SCO response centered at 250 K. For compound 2, the SCO is confirmed by variable temperature Mössbauer spectroscopy. In both cases, the anionic moieties are isolated from each other and so no electrical conductivity is observed.

Single-crystal structure analysis was required to correctly identify the mol­ecular structure and stereochemistry assignment of unexpected impurities in the preparation of a novel pharmaceutical spiro­cyclic imidazole-amine compound., During the racemization of a novel pharmaceutical spiro­cyclic imidazole–amine compound, namely, 6′-bromo-N-(6′-bromo-4-meth­oxy-4′′-methyl-3′H-di­spiro[cyclo­hexane-1,2′-indene-1′,2′′-imidazol]-5′′-yl)-4-meth­oxy-4′′-methyl-3′H-di­spiro­[cyclo­hexane-1,2′-indene-1′,2′′-imidazol]-5′′-imine, C36H41Br2N5O2, two impurities were isolated. These impurities were clearly dimers from mass spectroscopic analysis, however single-crystal diffraction characterization was required for the assignment of stereochemistry. The single-crystal diffraction results revealed subtly different structures to those proposed, due to an unexpected proton transfer. The dimers contain four stereocentres, but two of primary inter­est, and are centrosymmetric, so after careful structure refinement and close inspection it was possible to unambiguously assign the stereochemistry of both the homochiral [(S),(S)- and (R),(R)-] and the heterochiral [(S),(R)- and (R),(S)-] compounds.

Six substituted ligands based upon 2‐(naphthalen‐1‐yl)quinoline‐4‐carboxylate and 2‐(naphthalen‐2‐yl)quinoline‐4‐carboxylate have been synthesized in two steps from a range of commercially available isatin derivatives. These species are demonstrated to be effective cyclometalating ligands for Ir(III) yielding complexes of the form [Ir(C^N)2(bipy)]PF6 (where C^N = cyclometalating ligand; bipy = 2,2’‐bipyridine). X‐ray crystallographic studies on three examples demonstrate that the complexes adopt a distorted octahedral geometry wherein a cis‐C,C and trans‐N,N coordination mode is observed. Intra‐ligand torsional distortions are evident in all cases. The Ir(III) complexes display photoluminescence in the red part of the visible region (668‐693 nm) which is modestly tuneable via the ligand structure. The triplet lifetimes of the complexes are clearly influenced by the precise structure of the ligand in each case. Supporting computational (DFT) studies suggest that the differences in observed triplet lifetime are likely due to differing admixtures of ligand‐centred versus MLCT character instilled by the facets of the ligand structure. Triplet‐triplet annihilation upconversion (TTA‐UC) measurements demonstrate that the complexes based upon the 1‐naphthyl derived ligands are viable photosensitizers with upconversion quantum efficiencies of 1.6‐6.7%.

[Cu(en){B6O7(OH)6}].3H2O (1) (en = 1,2-diaminoethane), obtained as a crystalline solid in low yield (31%) after prolonged standing of an aqueous solution initially containing [Cu(en)2](OH)2 and B(OH)3 (1:7 ratio), was characterized by thermal analysis (TGA/DSC), 11B NMR and IR spectroscopy, powder XRD, and single-crystal XRD studies, and magnetic susceptibility measurements. The single-crystal X-ray diffraction revealed that the oxidoborate complex is a 1D coordination polymer with the hexaborate(2-) ligand bridging two hexacoordinate Cu(II) centers, in an alternating a fac-tridentate (κ3-O) and monodentate (κ1-O) arrangement. Cu-O coordination bonds and extensive H-bonding networks promote and stabilize the self-assembly of [Cu(en){B6O7(OH)6}].3H2O from the Dynamic Combinatorial Libraries of available reactants. [Cu(en){B6O7(OH)6}].3H2O is thermally decomposed to CuB6O10 in air at 700 °C.

[Cu(NH2CH2CH2NEt2){B6O7(OH)6}]·5H2O (1) and [Cu(NH3)2{B6O7(OH)6}]·2H2O (2) have been obtained as crystalline materials from aqueous solutions of Dynamic Combinatorial Libraries (DCLs) originating from B(OH)3 and appropriate Cu(II) amine complexes. These two Cu/O/B clusters are formed through self-assembly processes and contain tridentate hexaborate(2−)-κ3O ligands. Both compounds have been characterized by TGA/DSC, magnetic susceptibility measurements, IR spectroscopy, and single-crystal XRD studies. The intermolecular H-bond interactions between neighbouring hexaborate units are implicated in their templated synthesis. Compound 2 is a coordination polymer and stabilization is also gained through formation of an additional O–Cu coordinate bond. Steric congestion in 1 blocks formation of this bond resulting in insular complexes.

The solid-state behaviour of four alkali metal TCNQ complexes: (15-crown-5)LiTCNQ (1), (15-crown-5)NaTCNQ (2), (15-crown-5)Li(TCNQ)2.H2O (3.H2O) and (15-crown-5)Na(TCNQ)2.H2O (4.H2O) has been explored by single crystal X-ray diffraction, Infrared (IR), Raman and Electron Paramagnetic Resonance (EPR) measurements. The presence of a small cation and ionophore leads to subtle changes in behaviour compared with their larger alkali metal analogues and in the hydrated salts water bridges form links between the crown-encapsulated cations and neighbouring TCNQ stacks.

Authors thank the EPSRC for funding under grants EP/L012200/1 and EP/L012294/1. A new dual-chain oligothiophene-based organic semiconductor, EH-5T-TTC, is presented. The molecule contains two conjugated chains linked by a fused tetrathiocin core. X-ray crystallography reveals a boat conformation within the 8-membered sulfur heterocycle core and extensive π–π and intermolecular sulfur–sulfur interactions in the bulk, leading to a 2-dimensional structure. This unusual molecule has been studied as a ternary component in organic solar cell blends containing the electron donor PTB7-Th and both fullerene (PC71BM) and non-fullerene acceptors ITIC and EH-IDTBR. By incorporating EH-5T-TTC as a ternary component, the power conversion efficiency of the binary blends containing non-fullerene acceptor increases by 17% (from 7.8% to 9.2%) and by 85% for the binary blend with fullerene acceptor (from 3.3% to 6.3%). Detailed characterisation of the ternary blend systems implies that the ternary small molecule EH-5T-TTC functions differently in polymer:fullerene and polymer:non-fullerene blends and has dual functions of morphology modification and complementary spectral absorption. Publisher PDF

A series of six coordinate homoleptic and heteroleptic Cr(III) complexes have been formed that incorporate 8-quinolinato ligands. Three classes of complex have been synthesised and characterised: (i) [Cr(Q)3]; (ii) [Cr(Q)2(H2O)2]Cl; (iii) [Cr(Q)(N^N)2](PF6)2 (where Q is a ligand, 8-hydroxyquinoline, 8-hydroxy-2-methyl-quinoline, or 8-hydroxy-5-nitroquinoline; N^N = 1,10-phenanthroline or 2,2′-bipyridine). Single crystal X-ray structures were obtained for four complexes giving examples of [Cr(Q)2(H2O)2]Cl, two [Cr(Q)(bipy)2](PF6)2 and [Cr(Q)(phen)2](PF6)2. Each complex shows the ligands in the expected coordination mode with a distorted octahedral geometry evident at the metal centre. The UV–Vis. absorption data allowed assignments of the quinolinato-centred electronic transitions together with a much weaker spin allowed d–d transition (4A2 → 4T2) around 550 nm. Each complex was found to be luminescent in aerated MeCN solution at room temperature, which was attributed to a ligand-centred fluorescence based on the coordinated quinolinato ligand.

Intramolecular annulation reactions provide a powerful opportunity to access complex heterocyclic compounds with higher complexity than intermolecular conversions. This report details how, previously unknown fused dihydrobenzofuran-isoquinolone compounds, exhibiting an unusually strained shared aromatic unit, can be readily obtained from simply prepared benzamide derivatives bearing a tethered alkyne moiety, using copper C–H bond functionalisation catalysis. The mechanism has been proposed based on detailed DFT and topological analysis studies, and shows that the two key heterocycles are formed during distinct mechanistic steps; the dihydrobenzofuran arises from a migratory insertion and the isoquinolone from the following reductive elimination, resulting in an efficient Double Annulation Reaction (DAR). Actually, the results present an unprecedented migratory insertion of alkynes with benzamides when using copper as catalyst with the 8-aminoquinoline directing group and also study why the intermolecular variant is not operative.

The octahedral iron complex trans-[{O,O-(ƞ5-C5H4P(O)Ph2)2Fe}2Fe(III)Br2][Fe(III)Br4]has been prepared by self-assembly simply by adding anhydrous ferric chloride to a dichloromethane/methanol solution of dppf and 1,1,2,2-tetrabromoethane and then leaving to form a complex slowly. The key factor in the self-assembly is the addition of 1,1,2,2-tetrabromoethane which is the source of the bromide and is responsible for acid catalysed hydrolysis of ferric chloride.

The unusual [Cu7(NH3)2(H2O)4{B24O39(OH)12}]4− cluster anion, isolated in the form of its hydrated hydronium ion salt, has been crystallized in moderate yield (59%) through a templated self-assembly process from [Cu(NH3)4(H2O)2](OH)2 and B(OH)3 (10 equivalents) in aqueous solution. This novel anionic cluster is comprised of two diborate(2-) ligands bridging a linear {Cu3}6+ framework with this Cu3 fragment interacting with, and further supported by, a known larger [{Cu4O}B20O32(OH)8]6− cluster.

The stoichiometric reactions of amines with tri(4-chlorophenyl)boroxine (CPB) led to the formation of adducts CPB·L {L = morpholine (1a), benzylamine (1b) cyclohexylamine (1c), 2-picoline (1d), 4-picoline (1e), piperidine (1f)} and (CPB)2·(4,4′-trimethylenedipiperidine) (1g). Compounds 1a-1g have been characterized by NMR (11B, 1H, 13C), IR spectroscopy and powder-XRD. VT 1H NMR spectra on 1a and 1d-1g were consistent with a ligand exchange/recombination process and activation energies of 49–58 kJ mol-1 were obtained. The synthesis of [C6H11NMe3][Ph4B3O3] (2) from Ph2BOBPh2, PhB(OH)2 and [C6H11NMe3][OH] in a 1:4:2 ratio in MeOH/H2O is also reported. Compound 2 was characterized by thermal analysis (TGA/DSC), spectroscopy (IR, NMR) and 1a, 1b and 2 were further characterized by single-crystal XRD studies.

Three novel fluorescent aminophosphine ligands have been synthesised that incorporate napthyl (L1), pyrenyl (L2) and anthraquinone (L3) chromophores into their structures. The ligands react with [AuCl(tht)] (tht = tetrahydrothiophene) to give neutral complexes of the form [AuCl(L1-3)]. Solid state, X-ray crystallographic data was obtained for the anthraquinone derivative, [AuCl(L3)], and showed a distorted linear coordination geometry at Au(i). The packing structure also revealed a number of intermolecular π-π interactions that involve the anthraquinone and phenyl units of the aminophosphine ligand. 31P NMR spectroscopic data revealed δP values of +42.2 (L1), +42.1 (L2) and +26.1 (L3) ppm, which shifted downfield upon coordination to Au(i) to +64.6, +64.7, and +55.8 ppm, respectively. Supporting TD-DFT studies were able to reproduce the structure and 31P NMR chemical shifts of [AuCl(L3)] as well as rationalise the HOMO-LUMO compositions. Photophysical studies showed that the appended fluorophore dominates the absorption and emission properties for the ligands and complexes, with the anthraquinone derivatives showing visible emission at ca. 570 nm which was attributed to the intramolecular charge transfer character of the phosphinoaminoanthraquinone fragment.

The title compound, [(H3NCH2CH2NH2)Zn{κ3 O,O′,O′′-B12O18(OH)6-κ1 O′′′}Zn(en)(NH2CH2CH2NH3)]·8H2O (en=1,2-diaminoethane) (1), was prepared as a crystalline solid in moderate yield from the reaction of B(OH)3 with [Zn(en)3][OH]2 in aqueous solution (15:1) ratio. The structure contains a neutral bimetallic complex comprised of a unusual dodecaborate(6−) anion ligating two [H3NCH2CH2NH2Zn(en)n]3+ centers in a monodentate (n=1) or tridentate (n=0) manner.

New polyborate salts containing bulky non-metal cations have been prepared from either the free organic base or the [non-metal cation][OH] in methanolic aqueous solution: 1-adamantylammonium pentaborate [C10H18N][B5O6(OH)4] (1), 2-adamantylammonium pentaborate dihydrate [C10H18N][B5O6(OH)4].2H2O (2), N,N-dimethyl-1-adamantylammonium pentaborate.boric acid monohydrate [C12H22N][B5O6(OH)4].B(OH)3.H2O (3), N,N,N-trimethyl-1-adamantylammonium pentaborate trihydrate [C13H24N][B5O6(OH)4].3H2O (4), N,N,N-trimethyl-2-adamantylammonium pentaborate trihydrate [C13H24N][B5O6(OH)4].3H2O (5), dibenzylammonium pentaborate sesquihydrate [C14H16N][B5O6(OH)4].1.5H2O (6), bis(triphenylphosphine)iminium pentaborate sesquihydrate [C36H30NP2][B5O6(OH)4].1.5H2O (7), bis(triphenylphosphine)iminium triborate.2.5 hydrate [C36H30NP2][B3O3(OH)4].2.5H2O (8), 4,4'-bipiperidinium heptaborate dihydrate [C10H22N2][B7O9(OH)5].2H2O (9). All compounds were characterized by thermal (TGA/DSC), and spectroscopic analysis (NMR, IR). Compounds 3 - 5 and 9 have been characterized by single-crystal XRD studies. The waters of crystallization in 3 - 6 and the boric acid of crystallization in 3 play important structural roles in expanding the supramolecular pentaborate(1-) lattices to accommodate the bulkier cations.

A first generation machine-assisted approach towards the preparation of hybrid ligand/metal materials has been explored. A comparison of synthetic approaches demonstrates that incorporation of both flow chemistry and microwave heating, can be successfully applied to the rapid synthesis of a range of new phenyl-1H-pyrazoles (ppz) substituted with electron withdrawing groups (-F, -CF3, -OCF3, -SF5), and these, in turn, can be translated in to heteroleptic complexes, [Ir(ppz)2(bipy)]BF4 (bipy = 2,2’-bipyridine). Microwave-assisted syntheses for the IrIII complexes allows isolation of spectroscopically pure species in less than 1 hour of reaction time from IrCl3. All new complexes have been explored photophysically (including nanosecond time-resolved transient absorption spectroscopy), electrochemically and by TD-DFT studies which show that the complexes possess ligand-dependent, and thus, tuneable green-yellow luminescence (500-560 nm), with quantum yields in the range 5-15 %.

The synthesis of a number of pentaborate(1-) salts from cations arising from N-substituted &alpha, &alpha, &beta, and &alpha, &gamma, diaminoalkanes has been attempted in aqueous solution from B(OH)3 and the appropriate diammine in a 10:1 ratio. Despite relatively mild work-up conditions the pentaborate(1-) salts prepared were not always as anticipated and the following compounds were isolated in good yield: [Me2NH(CH2)2NHMe2][B5O6(OH)4]2 (1), [Et2NH(CH2)2NHEt2][B5O6(OH)4]2 (2), [Et2NH2][B5O6(OH)4] (3), [Me2NH2][B5O6(OH)4] (4), [Me2NH(CH2)3NHMe2][B5O6(OH)4]2 (5), [Et2NH(CH2)3NHEt2][B5O6(OH)4]2 (6), [Me3NCH2CH=CH2][B5O6(OH)4] (7), and [Me3N(CH2)3NMe3] [B5O6(OH)4]2.0.5H2O (8). The tetraborate(2-) salt, [Me3N(CH2)2NMe3][B4O5(OH)4].2B(OH)3.2H2O (9) was obtained in moderate yield (41%) from a 3:1 reaction of B(OH)3 with [Me3N(CH2)2NMe3](OH)2. All compounds were characterized by spectroscopy (1H, 11B, 13C NMR and IR) and thermal gravimetric analysis (TGA). BET analysis on materials derived thermally from selected samples (1, 2, 6, 7) all had porosities of &lt, 1 m2/g, demonstrating that they were non-porous. Single-crystal XRD structures were obtained for 2, 3, 7, 8 and 9 and all contain extensive H-bonded polyborate lattices.

The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC4) and N,N-di(pyridin-2-yl)decanamide (LC10) were combined with NCS− co-ligands to form the neutral heteroleptic Fe(II) complexes trans-[FeII(LC4)2(NCS)2] (1C4) and trans-[FeII(LC10)2(NCS)2] (1C10). Variable temperature crystallographic studies revealed that 1C4 is in the orthorhombic space group Pna21 between 85–200 K whereas 1C10 is in the monoclinic space group P21/c between 85–140 K. The average Fe–N bond lengths suggest that at 85 K 1C4 contains LS Fe(II) centres; however, the ca. 0.18 Å increase in the average Fe–N bond lengths between 85 and 120 K suggests a spin-transition to the HS state occurs within this temperature interval. 1C10 contains LS Fe(II) centres between 85 and 105 K. Upon warming from 105 to 140 K the average Fe–N bond lengths increase by ca. 0.19 Å, which suggests a spin-transition to the HS state. Solid-state magnetic susceptibility measurements showed that 1C4 undergoes semi-abrupt spin-crossover with T1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C10 undergoes an abrupt spin-crossover with T1/2 = 119.0 K, and is also accompanied by thermal hysteresis of ca. 4 K. The crystallographic and magnetic data show that the length of the complex's alkyl chain substituents can have a large impact on the structure of the crystal lattice as well as a subtle effect on the T1/2 value for thermal spin-crossover.

The synthesis of a number of pentaborate(1-) salts from cations arising from N-substituted α,α-, α,β-, and α,γ-diaminoalkanes has been attempted in aqueous solution from B(OH)3 and the appropriate diammine in a 10:1 ratio. Despite relatively mild work-up conditions the pentaborate(1-) salts prepared were not always as anticipated and the following compounds were isolated in good yield: [Me2NH(CH2)2NHMe2][B5O6(OH)4]2 (1), [Et2NH(CH2)2NHEt2][B5O6(OH)4]2 (2), [Et2NH2][B5O6(OH)4] (3), [Me2NH2][B5O6(OH)4] (4), [Me2NH(CH2)3NHMe2][B5O6(OH)4]2 (5), [Et2NH(CH2)3NHEt2][B5O6(OH)4]2 (6), [Me3NCH2CH=CH2][B5O6(OH)4] (7), and [Me3N(CH2)3NMe3] [B5O6(OH)4]2.0.5H2O (8). The tetraborate(2-) salt, [Me3N(CH2)2NMe3][B4O5(OH)4].2B(OH)3.2H2O (9) was obtained in moderate yield (41%) from a 3:1 reaction of B(OH)3 with [Me3N(CH2)2NMe3](OH)2. All compounds were characterized by spectroscopy (1H, 11B, 13C NMR and IR) and thermal gravimetric analysis (TGA). BET analysis on materials derived thermally from selected samples (1, 2, 6, 7) all had porosities of < 1 m2/g, demonstrating that they were non-porous. Single-crystal XRD structures were obtained for 2, 3, 7, 8 and 9 and all contain extensive H-bonded polyborate lattices.

The rapid development of Non-Fullerene Acceptors (NFAs) for organic solar cells has recently pushed the Power Conversion Efficiencies (PCE) over the 15% threshold, surpassing fullerene-based state-of-the-art devices. However, for the commercialization of large-scale photovoltaic modules, thick active layers films (150–300 nm) with high PCE and fill factors are required. The realization of materials with higher charge mobilities is fundamental for the roll-to-roll printing industry, and therefore understanding the factors that limit charge transport properties of NFAs becomes crucial for commercialization. The study of the molecular packing and arrangement of NFAs in the solid-state provides direct insight to the propensity of the pristine materials to crystallize and contribute efficiently to the charge transport. In this work we combine experimental techniques and molecular modelling, with the aim of analyzing the way in which NFAs interact in the solid-state and the key components of their structures for building efficient percolation pathways for charge transport. To this end, several new molecules were synthesized and crystallized by solvent vapour diffusion, which were then characterized by single crystal X-Ray Diffraction (XRD). These structures were further compared to a wide selection of literature materials. Density Functional Theory (DFT) calculations were also carried out to examine the electronic transport of these materials with respect to their molecular packing motifs.

The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC4) and N,N-di(pyridin-2-yl)decanamide (LC10) were combined with NCS− co-ligands to form the neutral heteroleptic Fe(II) complexes trans-[FeII(LC4)2(NCS)2] (1C4) and trans-[FeII(LC10)2(NCS)2] (1C10). Variable temperature crystallographic studies revealed that 1C4 is in the orthorhombic space group Pna21 between 85–200 K whereas 1C10 is in the monoclinic space group P21/c between 85–140 K. The average Fe–N bond lengths suggest that at 85 K 1C4 contains LS Fe(II) centres; however, the ca. 0.18 A increase in the average Fe–N bond lengths between 85 and 120 K suggests a spin-transition to the HS state occurs within this temperature interval. 1C10 contains LS Fe(II) centres between 85 and 105 K. Upon warming from 105 to 140 K the average Fe–N bond lengths increase by ca. 0.19 A, which suggests a spin-transition to the HS state. Solid-state magnetic susceptibility measurements showed that 1C4 undergoes semi-abrupt spin-crossover with T1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C10 undergoes an abrupt spin-crossover with T1/2 = 119.0 K, and is also accompanied by thermal hysteresis of ca. 4 K. The crystallographic and magnetic data show that the length of the complex's alkyl chain substituents can have a large impact on the structure of the crystal lattice as well as a subtle effect on the T1/2 value for thermal spin-crossover.

A series of four substituted benzo[g]quinoxaline species have been synthesised and utilised as cyclometalating ligands for iridium(III). The ligands (L1-L4) were synthesised and isolated in good yield following the condensation of 2,3-diaminonaphthalene with benzil and three of its derivatives. The substituent modulated electronic properties of L1-L4 were dominated by intraligand π−π* transitions, with the fluorescence profile demonstrating vibronic features attributed to the highly conjugated nature of the chromophore. Iridium(III) complexes of the form [Ir(L)2 (bipy)]PF6 were synthesised from L1-L4 in two steps. The electronic properties of the complexes reveal absorption in the UV-vis. region with spin forbidden metal-to-ligand charge transfer (MLCT) transitions possibly contributing at longer wavelengths to ca. 600 nm. Steady state luminescence (aerated, room temperature) on solutions of the complexes showed dual emissive properties in the visible and near-infra red (NIR) regions. Firstly, a vibronically structured emission in the visible region (ca. 525 nm) was attributed to ligand centred fluorescence (lifetime < 10 ns). Secondly, a broad emission peak in the NIR (ca. 950 nm) which extended to around 1200 nm was observed with corresponding lifetimes of 116–162 ns, indicative of triplet excited state emission.