Jonathan A. Kitchen

The influence of solvent polarity on the self‐assembly processes and its effect on the morphological outcome of self‐assembled aggregates is another domain that requires a comprehensive study. The present investigation aims to address these issues by employing a unique “V‐shaped” luminogen ( TBNap , N‐(3‐pyridyl)‐4‐amino‐1,8‐naphthalimide Tröger's base), where the two 1,8‐naphthalimide units are nearly orthogonal to each other. The TBNap is synthesized in high yield and fully characterized using standard characterization methods, including X‐ray diffraction analysis, which reveals distinctly different structural arrangements of TBNap crystallized as different solvates in various solvent media. Furthermore, due to its internal charge transfer nature, the TBNap exhibits positive solvatochromism and solvent‐guided morphogenesis. Given the unique structure, TBNap displays aggregation‐induced emission enhancement in THF‐H ₂ O medium and forms self‐assembled fluorescent nanoaggregates as imaged using different microscopic imaging techniques such as scanning electron microscopy (SEM) and confocal fluorescence microscopy. Furthermore, the latter is employed to demonstrate the in situ real‐time visualization of these fluorescent nanoaggregates formations in native conditions and correlate the morphological outcome with SEM imaging.

Designing and integrating Fe(III)-based spin crossover (SCO) complexes onto substrates remains a challenging goal with only a handful of examples reported. In this work, we successfully synthesized and characterized three [Fe(qsal-OR)₂]NO₃ (qsal-OR = 5-alkoxy-2-[(8-quinolylimino)methyl]phenolate) complexes, in which R = C₁₂H₂₅ 1, C₁₆H₃₃ 2, and C₂₂H₄₅ 3 to explore the impact of alkyl chain on the modulation of SCO activity and potential for self-assembly on a glass surface. The SCO is found to be gradual and incomplete in all cases, with the LS state more stabilised as the alkyl group shortens. We also demonstrate that all complexes form stable Langmuir films and achieve good transfer ratios to the glass surface, with 2 being the best in terms of stability. This paves the way for the SCO modulation of complexes in this class and the development of SCO devices.

The synthesis of a family of chiral and enantiomerically pure pyridyl‐diamide (pda) ligands that upon complexation with europium [Eu(CF₃SO₃)₃] result in chiral complexes with metal centered luminescence is reported; the sets of enantiomers giving rise to both circular dichroism (CD) and circularly polarized luminescence (CPL) signatures. The solid‐state structures of these chiral metallosupramolecular systems are determined using X‐ray diffraction showing that the ligand chirality is transferred from solution to the solid state. This optically favorable helical packing arrangement is confirmed by recording the CPL spectra from the crystalline assembly by using steady state and enantioselective differential chiral contrast (EDCC) CPL Laser Scanning Confocal Microscopy (CPL‐LSCM) where the two enantiomers can be clearly distinguished.

We report the synthesis of a new pyrene, dipicolinic acid‐based ligand (L₁H) and its corresponding multi‐emissive and multifunctional europium complex [Eu(L₁)₃] that is capable of single component color switchable emission from red to blue and also white. At high concentration (10 mM) the single component system results in near pure white emission (CIE coordinates x,y=0.329, 0.324). Furthermore, the system showed ratiometric oxygen sensing with oxygen significantly quenching the pyrene centered emission but not the Eu³⁺ emission, resulting in an overall emission color change from blue to red on increasing oxygen content.

White emissive and colour tunable films of a discrete multi-emissive 1,8-naphthalimide containing Ln³⁺ complex.

Multi-emissive compounds have attracted significant attention from the research community owing to the wide array of potential application areas. However, to move towards application, such systems should be readily immobilized by solution-based methods to form soft materials such as gels and films. Herein we report the use of Langmuir–Blodgett (LB) deposition to easily immobilize luminescent lanthanide-based amphiphilic solids into multi-emissive ultrathin LB films, by multilayering different luminescent amphiphiles. Utilizing this technique, we have reliably fabricated dual- and triple-emissive films where the overall emission from the film is tuned. Furthermore, we have demonstrated that these multi-emissive films are temperature-dependent, with emission profiles significantly altering from 294 to 340 K, resulting in colour changes and potential application as ultrathin, contactless ratiometric thermometer coatings.

Mixed deposition of amphiphilic Ln³⁺ complexes gives multi-emissive ultra-thin films.

The well-known lanthanide-binding motif, 2,6-pyridinedicarboxamide, has been functionalised with peripheral substituents using copper-catalysed azide alkyne coupling (CuAAC) to develop new symmetrical ‘clicked’ N₂,N₆-bis((1-(X)-1H-1,2,3,-triazol-4-yl)methyl)pyridine- 2,6-dicarboxamide (where X = ethyl (1) benzyl (2) and 2-naphthyl (3)). These ligands have been successfully coordinated with trivalent lanthanide ions (europium, terbium, and lanthanum) forming [Ln(L)₃](CF₃SO₃)₃ complexes. The ligands act as effective antennae for Eu³⁺ and Tb³⁺ complexes, which exhibit the characteristic sensitised emission profiles. The ability of 1–3 to assemble into 1:3 M:L systems in solution was investigated using UV-Vis, fluorescence, and NMR. Finally, density functional calculations of the ground state La³⁺ complexes have been carried out and show similar geometry and coordination parameters to those with available crystallographic data. The facile and modular synthesis of these ‘clicked’ PDC-based ligands makes these compounds excellent candidates for luminescent supramolecular materials development.

Seven readily synthesized 8-quinoline-4-R-3-thiosemicarbazone ligands [where R = phenyl (L₁H), 4-fluorophenyl (L₂H), 4-iodophenyl (L₃H), 4-nitrophenyl (L₄H), 4-carboxyphenyl (L₅H), 3-picolyl (L₆H), and octadecyl (L₇H)], and their corresponding Co(III) coordination complexes, [Co(L)₂]BF₄, have been synthesized and characterized. Crystallographic analysis of the complexes revealed that the substituents significantly alter solid-state supramolecular network topologies. The solution processability of these complexes was confirmed by incorporating a long carbon alkyl-chain into the ligand (L₇H) and immobilizing the complex onto quartz slides using Langmuir-Blodgett deposition. The facile and modular synthesis of these thiosemicarbazone-based ligands coupled with the potential to exploit multiple applications makes these compounds excellent candidates for functional supramolecular materials. Graphical Abstract

We report the synthesis, photophysical characterization, and biological evaluation of four DNA-binding ruthenium(II) polypyridyl 4-nitro- and 4-amino-1,8-naphthalimide conjugates. A meta arrangement around the ring connecting the 1,8-naphthalimide to a bipyridine ligand creates a cleft, the result of which renders the shape of the complex complementary to that of DNA. We have demonstrated that each complex exhibits water solubility and a distinctive set of photophysical properties that has allowed the nature of their interaction with DNA to be probed by various ground- and excited-state titrations. Furthermore, by varying the ancillary ligands, we also demonstrate their ability to act as DNA photocleavers, where all compounds have been found to cleave supercoiled DNA with high efficiency. Detailed cellular uptake experiments revealed that the conjugates accumulate in the cytoplasm and nucleus of HeLa cells, showing characteristic red metal-to-ligand charge-transfer emission, and also exhibit photoactivated cytotoxicity within the cells upon irradiation at 450 nm. A comparison between the meta and para arrangements of the 1,8-naphthalimide moiety relative to the Ru(II) center suggests increased DNA binding in the case of the meta arrangement; however, bipyridine–4-amino-1,8-naphthalimide conjugates appear to show superior phototoxicity in comparison to their 4-nitro derivatives.