Lignin is a common by-product of pulping industries. Diverse functional groups in the polymeric matrix make lignin a superior alternative for carbon-based materials. Meanwhile, porphyrin family is well known in multiple applications; however, aggregation-caused quenching (AQC) due to the strong π–π interaction in poor-solvent environments will limit the photoluminescence intensity of porphyrin. In this study, a new lignin-porphyrin (AL–CTPP) polymer was developed, which combined and promoted the functionalities of the two chemicals. In photoluminescence investigations, the emission intensity of AL–CTPP in the 600 to 780 nm region was 30-fold stronger than that of porphyrin alone when the water fraction (f_w) > 0.9. Lignin served as a stable backbone immobilizing porphyrin and prevented unwanted aggregation of porphyrin and the related aggregation-caused quenching in high f_w solution at various pH. Furthermore, linear correlations were established between absorption properties of AL–CTPP with concentrations of five metal ions (i.e., Mn²⁺, Ni²⁺, Co²⁺, Cu²⁺, and Zn²⁺). With these unique features, AL–CTPP showed enhanced performance for potential bio-imaging and environmental applications. Lignin-porphyrin polymers may represent a significant potential product of biorefineries and the effective utilization of lignin to fabricate a new functional material which offers significant benefits to support waste valorization.

A series of luminescent isocyanorhenium(I) complexes with chelating acyclic diaminocarbene ligands (N^C) has been synthesized and characterized. Two of these carbene complexes have also been structurally characterized by X-ray crystallography. These complexes show blue-to-red phosphorescence, with the emission maxima not only considerably varied with a change in the number of ancillary isocyanide ligands but also extremely sensitive to the electronic and steric nature of the substituents on the acyclic diaminocarbene ligand. A detailed study with the support of density functional theory calculations revealed that the lowest-energy absorption and phosphorescence of these complexes in a degassed CH₂Cl₂ solution are derived from the predominantly metal-to-ligand charge-transfer [dπ(Re) → π*(N^C)] excited state. The unprecedented anion-binding and CO₂-capturing properties of the acyclic diaminocarbene have also been described.

A series of lanthanide (Ln) compounds, [Eu^III(L)₂(MeOH)(H₂O)](ClO₄)₃ (1), [Tb^III(L)₂(H₂O)](Cl₃) (2) and [M^III(L)₂(NO₃)](ClO₄)₂ (M = Eu (3); Sm (4); Tb (5); Dy (6)), have been prepared by the treatment of a neutral tetra-dentate ligand (N²,N⁹-dibutyl-1,10-phenanthroline-2,9-dicarboxamide, L) with various Ln(III) salts in MeOH. All of the compounds have been structurally characterized by X-ray crystallography. It is noted that the anions of the Ln(III) salts play crucial roles in the solid-state structures and the properties of the resulting complexes. In compounds 1 and 2, the metal centres are 10- and 9-coordinated, respectively, which are surrounded by two L ligands and solvent molecules. When the nitrate salts are used instead, four isostructural 10-coordinate Ln(III) compounds are obtained. The photophysical properties show that most of the compounds exhibit the characteristic emission peaks of Ln(III). Ligand L acts as a very good ‘antenna’ to sensitize the Eu(III) emission, but not for other Ln(III) emissions. The quantum yield of 3 is 75.4%, which is much higher than that of 1 (17.6%) due to the –OH oscillators of the coordinated H₂O and MeOH molecules in 1. The magnetic properties of the Tb(III) compounds 2 and 5 and the Dy(III) compound 6 were investigated in detail as a natural extension of our previous study of the effect of high-coordination number on the single-ion magnet (SIM) behaviour of 3d compounds. The results show that subtle changes in the coordination environment have significant effects on the magnetic behaviour. The 9-coordinate compound 2 is not a single ion magnet (SIM), but both 10-coordinate compounds 5 and 6 exhibit field-induced SIM behaviour. It is also interesting to note that, upon the application of a small dc field, 5 exhibits two distinct relaxation processes, which is uncommon in Ln-based SIMs.