A New Decaoxidooctaborate(2−) Anion, [B₈O₁₀(OH)₆]^2–: Synthesis and Characterization of [Co(en)₃][B₅O₆(OH)₄][B₈O₁₀(OH)₆)]·5H₂O (en = 1,2-Diaminoethane)

The synthesis and X-ray diffraction structure of [Co­(en)₃]­[B₅O₆(OH)₄]­[B₈O₁₀(OH)₆]·5H₂O (<b>1</b>) are reported. Compound <b>1</b> arises through a selective-templating process from a Dynamic Combinatorial Library of polyborate anions. Compound <b>1</b> contains two different polyborate species, with [B₈O₁₀(OH)₆]^2– being particularly novel. It is comprised of fused tetraborate and pentaborate anions with a 4-coordinate B atom and a 3-coordinate O atom in common

Phosphorescent, Cyclometalated Cinchophen-Derived Platinum Complexes: Syntheses, Structures, and Electronic Properties

The syntheses of nine new monometallic heteroleptic platinum complexes [Pt­(<b>L1–4</b>)­(acac)], [Pt­(<b>L1</b>)­(hmacac/hfacac)], [PtCl­(<b>L1</b>)­(py)], [Pt­(<b>L1</b>)­(8-Q)], [Pt­(<b>L1</b>)­(bpy)]­(PF₆) (where L1 = 2-phenyl-4-ethyl-quinolinecarboxylate; L2/L3 = <i>N</i>-functionalization of 2-phenyl-<i>N</i>-aryl/alkyl-quinoline-4-carboxamides; L4 = 2-phenyl-4-quinolinecarboxylic acid (cinchophen); acac = acetylacetonato; hmacac =2,2,6,6-tetramethyl-3,5-heptanedionate; hfacac = hexafluoroacetylacetonate; py = pyridine; 8-Q = 8-quinolinato; bpy =2,2′-bipyridine) are described from precursor dimeric Pt­(II) species via an intermediate DMSO adduct of the general form [PtCl­(<b>L1–4</b>)­(DMSO)]. Single crystal X-ray diffraction studies were undertaken on three complexes, [Pt­(<b>L1</b>)­(acac)], [PtCl­(<b>L1</b>)­(DMSO)], and [Pt­(<b>L1</b>)­(bpy)]­(PF₆). The structures show that the complexes each adopt a distorted square planar geometry (most severely in the case of [Pt­(<b>L1</b>)­(bpy)]­(PF₆)) with indications of intermolecular Pt–Pt interactions in one example. The complexes were investigated using ¹⁹⁵Pt­{¹H} NMR spectroscopy, revealing varied chemical shifts that were strongly dependent upon the specific coordination environment of Pt­(II). Luminescence studies showed the complexes possess a phosphorescent character with tunable emission wavelengths between 605 and 641 nm and luminescent lifetimes up to ∼450 ns. Supporting TD-DFT studies provided descriptions of the HOMO and LUMO energy levels of the key complex types, confirming an MLCT contribution to the lowest energy absorption that generally correlated well with the experimental spectra. The contribution of the Pt­(5d) center to the calculated HOMOs was strongly ligand dependent, whereas the LUMOs are generally localized over the quinoline component of the cyclometalated ligand

Facile Synthesis of Novel Functionalized Silsesquioxane Nanostructures Containing an Encapsulated Fluoride Anion

The presence of strongly electron withdrawing groups on alkoxysilanes, EWG-(CH₂)_<i>n</i>-Si­(OEt)₃ (where <i>n</i> = 1–3 and the electron-withdrawing group EWG contains an Si–C­(sp³) bond), facilitates the formation and encapsulation of the fluoride anion in a silsesquioxane cage. Such species have been studied by ¹⁹F and ²⁹Si NMR spectroscopy and X-ray crystallography together with MALDI-TOF and ESI mass spectrometry. The EWG must not be a good leaving group. Interestingly, this strategy led only to the T₈ cage and excellent yields were obtained (81–95%) even without solvent. A wide range of functionalities were used. This new route offers an opportunity to build novel nanometer-sized 3-D molecular structures with a variety of functionalities which have not been accessible in the past

Facile Synthesis of Novel Functionalized Silsesquioxane Nanostructures Containing an Encapsulated Fluoride Anion

The presence of strongly electron withdrawing groups on alkoxysilanes, EWG-(CH₂)_<i>n</i>-Si­(OEt)₃ (where <i>n</i> = 1–3 and the electron-withdrawing group EWG contains an Si–C­(sp³) bond), facilitates the formation and encapsulation of the fluoride anion in a silsesquioxane cage. Such species have been studied by ¹⁹F and ²⁹Si NMR spectroscopy and X-ray crystallography together with MALDI-TOF and ESI mass spectrometry. The EWG must not be a good leaving group. Interestingly, this strategy led only to the T₈ cage and excellent yields were obtained (81–95%) even without solvent. A wide range of functionalities were used. This new route offers an opportunity to build novel nanometer-sized 3-D molecular structures with a variety of functionalities which have not been accessible in the past

Efficient, Scalable, and Solvent-free Mechanochemical Synthesis of the OLED Material Alq₃ (q = 8‑Hydroxyquinolinate)

The aluminum complex Alq₃ (q = 8-hydroxyquinolinate), which has important applications in organic light-emitting diode materials, is shown to be readily synthesized as a pure phase under solvent-free mechanochemical conditions from Al­(OAc)₂OH and 8-hydroxyquinoline by ball milling. The initial product of the mechanochemical synthesis is a novel acetic acid solvate of Alq₃, and the α polymorph of Alq₃ is obtained on subsequent heating/desolvation of this phase. The structure of the mechanochemically prepared acetic acid solvate of Alq₃ has been determined directly from powder X-ray diffraction data and is shown to be a different polymorph from the corresponding acetic acid solvate prepared by solution-state crystallization of Alq₃ from acetic acid. Significantly, the mechanochemical synthesis of Alq₃ is shown to be fully scalable across two orders of magnitude from 0.5 to 50 g scale. The Alq₃ sample obtained from the solvent-free mechanochemical synthesis is analytically pure and exhibits identical photoluminescence behavior to that of a sample prepared by the conventional synthetic route

Efficient, Scalable, and Solvent-free Mechanochemical Synthesis of the OLED Material Alq₃ (q = 8‑Hydroxyquinolinate)

The aluminum complex Alq₃ (q = 8-hydroxyquinolinate), which has important applications in organic light-emitting diode materials, is shown to be readily synthesized as a pure phase under solvent-free mechanochemical conditions from Al­(OAc)₂OH and 8-hydroxyquinoline by ball milling. The initial product of the mechanochemical synthesis is a novel acetic acid solvate of Alq₃, and the α polymorph of Alq₃ is obtained on subsequent heating/desolvation of this phase. The structure of the mechanochemically prepared acetic acid solvate of Alq₃ has been determined directly from powder X-ray diffraction data and is shown to be a different polymorph from the corresponding acetic acid solvate prepared by solution-state crystallization of Alq₃ from acetic acid. Significantly, the mechanochemical synthesis of Alq₃ is shown to be fully scalable across two orders of magnitude from 0.5 to 50 g scale. The Alq₃ sample obtained from the solvent-free mechanochemical synthesis is analytically pure and exhibits identical photoluminescence behavior to that of a sample prepared by the conventional synthetic route

Alkynyl-naphthalimide Fluorophores: Gold Coordination Chemistry and Cellular Imaging Applications

A range of fluorescent alkynyl-naphthalimide fluorophores has been synthesized and their photophysical properties examined. The fluorescent ligands are based upon a 4-substituted 1,8-naphthalimide core and incorporate structural variations (at the 4-position) to tune the amphiphilic character: chloro (<b>L1</b>), 4-[2-(2-aminoethoxy)­ethanol] (<b>L2</b>), 4-[2-(2-methoxyethoxy)­ethylamino] (<b>L3</b>), piperidine (<b>L4</b>), morpholine (<b>L5</b>), 4-methylpiperidine (<b>L6</b>), and 4-piperidone ethylene ketal (<b>L7</b>) variants. The amino-substituted species (<b>L2</b>–<b>L7</b>) are fluorescent in the visible region at around 517–535 nm through a naphthalimide-localized intramolecular charge transfer (ICT), with appreciable Stokes’ shifts of ca. 6500 cm^–1 and lifetimes up to 10.4 ns. Corresponding two-coordinate Au­(I) complexes [Au­(L)­(PPh₃)] were isolated, with X-ray structural studies revealing the expected coordination mode via the alkyne donor. The Au­(I) complexes retain the visible fluorescence associated with the coordinated alkynyl-naphthalimide ligand. The ligands and complexes were investigated for their cytotoxicity across a range of cell lines (LOVO, MCF-7, A549, PC3, HEK) and their potential as cell imaging agents for HEK (human embryonic kidney) cells and Spironucleus vortens using confocal fluorescence microscopy. The images reveal that these fluorophores are highly compatible with fluorescence microscopy and show some clear intracellular localization patterns that are dependent upon the specific nature of the naphthalimide substituent

Fluorescent Rhenium-Naphthalimide Conjugates as Cellular Imaging Agents

A range of biologically compatible, fluorescent rhenium-naphthalimide conjugates, based upon the rhenium <i>fac</i>-tricarbonyl core, has been synthesized. The fluorescent ligands are based upon a N-functionalized, 4-amino-derived 1,8-naphthalimide core and incorporate a dipicolyl amine binding unit to chelate Re­(I); the structural variations accord to the nature of the alkylated imide with ethyl ester glycine (<b>L</b>^<b>1</b>), 3-propanol (<b>L</b>^<b>2</b>), diethylene glycol (<b>L</b>^<b>3</b>), and benzyl alcohol (<b>L</b>^<b>4</b>) variants. The species are fluorescent in the visible region between 505 and 537 nm through a naphthalimide-localized intramolecular charge transfer, with corresponding fluorescent lifetimes of up to 9.8 ns. The ligands and complexes were investigated for their potential as imaging agents for human osteoarthritic cells and protistan fish parasite <i>Spironucleus vortens</i> using confocal fluorescence microscopy. The results show that the specific nature of the naphthalimide structure serves to control the uptake and intracellular localization of these imaging agents. Significant differences were noted between the free ligands and complexes, with the Re­(I) complex of <b>L</b>^<b>2</b> showing hydrogenosomal localization in <i>S. vortens</i>

Metal–Organic Frameworks Constructed from Group 1 Metals (Li, Na) and Silicon-Centered Linkers

A series of “light metal” metal–organic frameworks containing secondary building units (SBUs) based on Li⁺ and Na⁺ cations have been prepared using the silicon-centered linkers Me_<i>x</i>Si­(<i>p</i>-C₆H₄CO₂H)_4‑<i>x</i> (<i>x</i> = 2, 1, 0). The unipositive charge, small size, and oxophilic nature of the metal cations give rise to some unusual and unique SBUs, including a three-dimensional nodal structure built from sodium and oxygen ions when using the triacid linker (<i>x</i> = 1). The same linker with Li⁺ cations generated a chiral, helical SBU, formed from achiral starting materials. One-dimensional rod SBUs are observed for the diacid (<i>x</i> = 2) and tetra-acid (<i>x</i> = 0) linkers with both Li⁺ and Na⁺ cations, where the larger size of Na⁺ compared to Li⁺ leads to subtle differences in the constitution of the metal nodes

Fluorescent Rhenium-Naphthalimide Conjugates as Cellular Imaging Agents

A range of biologically compatible, fluorescent rhenium-naphthalimide conjugates, based upon the rhenium <i>fac</i>-tricarbonyl core, has been synthesized. The fluorescent ligands are based upon a N-functionalized, 4-amino-derived 1,8-naphthalimide core and incorporate a dipicolyl amine binding unit to chelate Re­(I); the structural variations accord to the nature of the alkylated imide with ethyl ester glycine (<b>L</b>^<b>1</b>), 3-propanol (<b>L</b>^<b>2</b>), diethylene glycol (<b>L</b>^<b>3</b>), and benzyl alcohol (<b>L</b>^<b>4</b>) variants. The species are fluorescent in the visible region between 505 and 537 nm through a naphthalimide-localized intramolecular charge transfer, with corresponding fluorescent lifetimes of up to 9.8 ns. The ligands and complexes were investigated for their potential as imaging agents for human osteoarthritic cells and protistan fish parasite <i>Spironucleus vortens</i> using confocal fluorescence microscopy. The results show that the specific nature of the naphthalimide structure serves to control the uptake and intracellular localization of these imaging agents. Significant differences were noted between the free ligands and complexes, with the Re­(I) complex of <b>L</b>^<b>2</b> showing hydrogenosomal localization in <i>S. vortens</i>