Effect of solvent inclusion on the structures and solid-state fluorescence of coordination compounds of naphthalimide derivatives and metal halides

The structural characteristics and solid-state fluorescence of coordination compounds formed between the fluorophore N-((3-pyridyl)methyl)-1,8-naphthalimide (3-pn) and a range of divalent metal halides, were investigated. Six new crystal structures, of the formula ML 2 X 2.solv, were obtained through the combination of the organic ligand L = 3-pn with the divalent metal halides CoX2 (X = Cl− or Br−) or ZnX2 (X = Cl− or Br−) in different solvents. It was found that solvent molecules are incorporated into all the structures, and that the same complex can incorporate different solvent molecules. The conformation of the complex molecule is determined by the solvent molecule incorporated into the structure. The fluorescence intensity is affected by the identity of the metal and halido ligand in the complex molecule, while the identity of the solvent molecule and the metal ion affects the emission wavelength. Thus, the solvent of crystallisation impacts on the solid-state fluorescence of the compounds, hence the same complex can be made to fluoresce at different wavelengths depending on the solvent of crystallisation.

Naphthalimide derivatives as fluorescent probes for imaging endogenous gasotransmitters

Gasotransmitters have gained significant recognition attributed to their evident biological impacts, and is accepted as a promising and less-explored area with immense research scope. The three-member family comprising of nitric oxide, carbon monoxide and hydrogen sulphide as endogenous gaseous signaling molecules have been found to elicit a plethora of crucial biological functions, spawning a new research area. The sensing of these small molecules is vital to gain deeper insights into their functions, as they can act both as a friend or a foe in mammalian systems. The initial sections of the review present the physiological and pathophysiological roles of these endogenous gas transmitters and their synergistic interactions. Further, various detection approaches, especially the usage of fascinating features of 1,8-naphthalimide as fluorescent probe in the detection and monitoring of these small signaling molecules are highlighted. The current limitations and the future scope of improving the sensing of the three gasotransmitters are also discussed.

Fluorescent 4-amino-1,8-naphthalimide Tröger's bases (TBNaps) possessing (orthogonal) 'α-amino acids', esters and di-peptides and their solvent dependent photophysical properties

The synthesis of fifteen luminescent bis-naphthalimide based Tröger's bases (TBNaps) derived from 4-amino-1,8-naphthalimide (4-Amino-Nap) precursors is described; these scaffolds possess α-amino acids, esters or di-peptides conjugated at the imide site and show minor fluorescence in aqueous solution while being highly emissive in organic solvents. The investigation shows that these TBNaps possessing ICT excited state properties are capable of generating either positive or negative solvatochromic effects in response to changes in polarity and/or the hydrogen bonding capabilities of the medium.

Balancing connectivity with function in silver(i) networks of pyridyltriazole (tzpa) ligands results in the formation of a metallogel

A new flexible and divergent 1,2,3-triazol-4-yl-picolinamide (tzpa) ligand 2 and the half-equivalent model ligand 1, both functionalised with pendant 3-pyridyl groups, are reported and their coordination behaviour with silver(i) ions is explored, both in the crystalline phase and through the formation of a supramolecular metallogel. The self-assembly of tzpa ligand 1 with AgCF3SO3 resulted in the formation of a 1D coordination polymer, binding in a bidentate fashion through the pyridyl and triazole nitrogen atoms of the tzpa binding site and a pendant pyridyl nitrogen atom of an adjacent ligand. Doubling the number of metal binding sites in ligand 2, while retaining the same metal binding domain, gives rise to the formation of a supramolecular metallogel on reaction with AgBF4 at 5 wt% in MeCN, possessing self-healing properties.

Fluorescent supramolecular hierarchical self-assemblies from glycosylated 4-amino- and 4-bromo-1,8-naphthalimides

The investigation into the self-assembly formation of the glycan based 4-amino- and 4-bromo-1,8-naphthalimide (Nap) structures1–3is presented.

Unexpected linkage isomerism in chiral tetranuclear bis-tridentate (1,2,3-triazol-4-yl)-picolinamide (tzpa) grids

The synthesis of a chiral bis-tridentate (1,2,3-triazol-4-yl)-picolinamide (tzpa) ligand is described and its coordination chemistry with Cu(NO3)2 and [Cu(MeCN)4]PF6 is explored in the crystalline phase as well as in solution. Chiral [2 × 2] tetranuclear square grid complexes [Cu4(H21)4](NO3)8 and [Cu4(H1)4](PF6)4 were observed, and crystallographically analysed, these being linkage isomers with N4O2 and N5O coordination spheres, respectively. These come about by an unusual in situ amide deprotonation and coordination, which accompanies a CuI → CuII oxidation process.

Luminescent lanthanide (Eu(iii)) cross-linked supramolecular metallo co-polymeric hydrogels: the effect of ligand symmetry

Two lanthanide luminescent naphthyl-dipicolinic amide (dpa) methacrylate monomers for the synthesis of grafted supramolecular co-polymer gels (hydrogels), and their use as additional crosslinks in robust covalently cross-linked HEMA hydrogels is presented.

Glycosylated naphthalimides and naphthalimide Tröger's bases as fluorescent aggregation probes for Con A

We report the synthesis of glycosylated naphthalimide compounds and their application as fluorescent probes for Concanavalin A (Con A) lectin.

Crystallographic studies of 2-picolyl substituted naphthalene diimide and bis-phthalimide ligands and their supramolecular coordination chemistry

The coordination chemistry of two 2-picolyl substituted bis-imide ligands is explored, revealing fascinating metallosupramolecular assemblies but an apparent barrier to chelation compared to monoimide congeners.

Norbornene chaotropic salts as low molecular mass ionic organogelators (LMIOGs)

Phenylalanine functionalised norbornene (9:Na) functions as a potent, low molecular-mass (MW = 333 Da) ionic organogelator with a minimum gelating concentration of 0.5 wt% in THF, i-PrOH, 1,4-dioxane and n-BuOH. Fibrous crystals form in the gel and X-ray crystallography identified a cation mediated helical assembly process controlled by the chirality of the phenylalanine. In addition to excellent gelating properties 9:Na readily forms aqueous biphasic and triphasic systems.

Exploring the reversible host–guest chemistry of a crystalline octanuclear Ag(i) metallosupramolecular macrocycle formed from a simple pyrazinylpyridine ligand

High nuclearity Ag(i) assemblies are prepared from simple polytopic ligands, including an octanuclear metallomacrocycle which exhibits reversible and selective guest exchange.

A folded [2 × 2] metallo-supramolecular grid from a bis-tridentate (1,2,3-triazol-4-yl)-picolinamide (tzpa) ligand

A flexible ditopic ligand 1 containing two N,N,O-tridentate (1,2,3-triazol-4-yl)-picolinamide chelating pockets is reported and the formation of multimetallic architectures is explored in the solid and the solution phase. The self-assembled Zn^II complex [Zn₄(1)₄](ClO₄)₈ exhibited a folded [2 × 2] square grid supramolecular architecture that selectively assembled in MeCN solution as shown using various spectroscopic techniques. The closely related Fe^II complex shows equivalent behaviour in the solid state, while a discrete dinuclear species [Cu₂(NO₃)₄1]·5MeCN was the sole product observed in the solid state from the reaction between 1 and Cu^II under similar conditions.

Naphthalimide-based fluorescent gelator for construction of both organogels and stimuli-responsive metallogels

Herein, we presented the first example that a gelator can form both organogels and metallogels with multiple gelation approaches tuned by multiple stimuli.

One-pot facile synthesis of 4-amino-1,8-naphthalimide derived Tröger's bases via a nucleophilic displacement approach

We report here a novel one-pot synthetic strategy for the synthesis of a family of N-alkyl-1,8-naphthalimide derived Tröger's bases (in overall yield of 65–96%) via a nucleophilic substitution reaction.

Competing phenol–imidazole and phenol–phenol interactions in the flexible supramolecular environment of N,N′-bis(3-imidazol-1-ylpropyl)naphthalenediimide causing domain expansion

Spectroscopic and crystallographic studies on cocrystals of N,N′-bis(3-imidazol-1-yl-propyl)naphthalenediimide (L) with a series of phenolic compounds have revealed that competition to form phenol–imidazole and phenol–phenol synthons causes domain expansion.

Supramolecular coordination polymers using a close to ‘V-shaped’ fluorescent 4-amino-1,8-naphthalimide Tröger's base scaffold

A novel 4-amino-1,8-naphthalimide derived Tröger's base ligand L has been synthesised and subsequently used in the formation of two new supramolecular coordination polymers TB-Co-CP and TB-Cd-CP.

A resilient and luminescent stimuli-responsive hydrogel from a heterotopic 1,8-naphthalimide-derived ligand

A heterotopic naphthalimide ligand N-(4-picolyl)-4-(4′-carboxyphenoxy)-1,8-naphthalimide HL is utilised for the formation of self-assembled soft materials.