Near‐Infrared Phosphorescent Supramolecular Alkyl/Aryl‐Iridium Porphyrin Assemblies by Axial Coordination

Abstract

Five-coordinated d metal complexes are relatively uncommon but can be useful building blocks for the construction of supramolecular assemblies. In this work we have used the strong trans effect of aryl and alkyl ligands for the synthesis of luminescent five-coordinated organoiridium porphyrins, which are useful building blocks for the construction of metallamacrocycles and metallacages of iridium through metal-ligand interactions at the axial positions of iridium porphyrins (Ir(por)). Diverse di- or tritopic aryl or alkyl linkers were employed as the axial ligands to coordinate Ir(por) at an axial position to afford di- or trinuclear five-coordinated [{Ir(ttp)} (X)] (ttp=5,10,15,20-tetrakis(p-tolyl)porphyrinato(2-); n=2, X=diaryl; n=3, X=trialkyl). [{Ir(ttp)} (X)] could be further coordinated with ditopic isocyanide or pyridine ligands at the other axial site of each Ir(ttp) to give unprecedented cyclic supramolecular metalloporphyrin assemblies, including tetra- and hexanuclear metallamacrocycles and hexanuclear metallacages. The Ir(por) metallamacrocycles and metallacages display phosphorescence in the near-infrared region with quantum yields of around 2 % and microsecond emission lifetimes.

Recent advances on the construction of long-wavelength emissive supramolecular coordination complexes for photo-diagnosis and therapy

“…However, the excitation/emission wavelengths of most conventional SCCs predominantly fall within the ultraviolet-visible (200-700 nm) and first near-infrared (NIR-I, 700-900 nm) regions. [44][45][46][47][48][49][50][51][52][53][54][55] The shorter excitation/emission wavelengths often result in suboptimal imaging quality and less effective treatment due to factors such as scattering and tissue absorption, auto-fluorescence, and limited depth penetration. [56][57][58] Fortunately, fluorescent ligands in the second near-infrared region (NIR-II, 1000-1700 nm) offer notable advantages, including deep tissue penetration facilitated by their ultra-long wavelengths, thereby overcoming the inherent limitations of conventional fluorescence imaging.…”

Coordination-Driven Self-Assembly of Cyclometalated Iridium Squares Using Linear Aromatic Diisocyanides

“…The cyclometalating ligands were chosen to vary the triplet energy of the bis-cyclometalated iridium node, descending in the order 2-phenylpyridine (ppy), 2-phenylbenzothiazole (bt), and 1-phenylisoquinoline (piq). Linear diisocyanides of the type described here have been used in surface chemistry − and as bridging ligands for multimetallic structures, − but their application in coordination-driven self-assembly is underexplored. We used three different linear aryl diisocyanides with varying spacer lengths in this study.…”

“…We used three different linear aryl diisocyanides with varying spacer lengths in this study. Commercially available 1,4-phenylene diisocyanide (PDI) and the known compound 4,4′-diisocyano-1,1′-biphenyl (BPDI) have been previously described, − and we also introduce here the new ligand 1,1′-(1,2-ethynediyl)­bis­(4-isocyanobenzene) (EDI) with a longer π-conjugated linker between the two isocyanides. Our hypothesis is that bridging isocyanides offer several potential synthetic advantages in the assembly of polynuclear complexes with cyclometalated iridium building blocks.…”

Positional Isomers of Isocyanoazulenes as Axial Ligands Coordinated to Ruthenium(II) Tetraphenylporphyrin: Fine-Tuning Redox and Optical Profiles

“…Organic isocyanides, CN–R, are important constituents in coordination chemistry’s ligand toolbox, particularly because of their tunable steric and σ-donor/π-acceptor ratio characteristics. − Whereas the coordination of organic isocyanides to a variety of metalloporphyrins − and metallophthalocyanines − has been well-documented, combining redox noninnocent organic and organometallic isocyanides with such transition metal platforms offers additional distinct opportunities in the design of molecular wires. − Indeed, axial coordination of isocyanoferrocene and 1,1′-diisocyanoferrocene to Ru­(II)­porphyrins and phthalocyanines has been recently shown to exert unusual redox profiles of the corresponding adducts that are attractive in the context of applications in molecular electronics, including molecular wires. , Isocyanoazulenes constitute a special class of isocyanoarenes and feature the non-benzenoid aromatic substituent comprising fused five- and seven-membered sp 2 -carbon rings. The polar nature of the azulenic scaffold (ca.…”

“…NC), 7.32 (t, 2H, H6 , C 10 H 7 NC,3 J H−H = 9.8 Hz),6.91 (t, H5,7 , C 10 H 7 NC, 3 J H−H = 9.8 Hz), 5.32 (s, 4H, H 1,3 , C 10 H 7 NC) ppm. IR (KBr): ν(NC) 2067 cm −1 .…”