Core substituted naphthalene diimide – metallo bisterpyridine supramolecular polymers: synthesis, photophysics and morphology

Abstract

A series of metallo Ru(ii), Fe(ii), Co(ii) bisterpyridine polymers were prepared with naphthalene diimide (NDI) groups inserted between two 4'-phenyl-2,2:6',2''-terpyridine (phtpy) groups. Core-substituted NDIs typically have long-lived excited states with relatively high quantum yields, yet the NDI emission in these metallopolymers was completely quenched, most likely because of efficient electron-transfer from the M(phtpy)2(2+) groups to the excited NDIs. AFM, TEM and SEM experiments indicate that the regiochemistry of the substitution on the core of the naphthalene diimide, together with coordination of the terpyridine ligand to different metals, strongly influences the morphologies of the resulting metallosupramolecular polymers. The morphologies of spin-coated samples of the para-substituted polymers revealed the formation of long, bundled nanorods. Lengths on the order of ∼8 μm were observed for the bundle of the longest polymers (-Ru) by both AFM and TEM microscopy. The morphologies of the meta substituted polymers, on the other hand, exhibited significantly shorter and less well-defined morphologies.

Spacer Conjugation and Surface Support Effects in Monolayer Electrochromic Materials

“…The MLCT band of the [Fe 2+ (s-tpy) 2 ] complex where pyr and ph-tpy moieties of the ligand are connected through a nonconjugated single-bond linker appears at 568 nm, identical to the previously reported MLCT band of [Fe 2+ (ph-tpy) 2 ] centered at 568 nm. 53 Moreover, N-methylation of the pyr moiety has no influence on the MLCT band of [Fe 2+ (CH 3 -stpy) 2 ]I 2 (BF 4 ) 2 observed at 568 nm. On the contrary, the introduction of a conjugated linker leads to a red shift of the MLCT bands of [Fe 2+ (d-tpy) 2 ](BF 4 ) 2 and [Fe 2+ (t-tpy) 2 ]-(BF 4 ) 2 to 574 nm.…”

Functional Naphthalene Diimides: Synthesis, Properties, and Applications

“…The NDI emission in these metallopolymers was completely quenched, which may be due to an efficient electron transfer from the M­(phtpy) 2 2+ groups to the excited states of NDIs. SEM and TEM analysis clearly shows the formation of bundled nanorods with lengths of the order of ∼8 μm . Liu et al reported the syntheses and structures of three isostructural 1D NDI based supramolecular coordination networks, and upon the lone pair−π interactions between the capped halogen atoms and electron-deficient NDI, furthermore, the NDI based coordinated network exhibited different photochromic behaviors upon photoiradiation …”

Core-Substituted Naphthalene-Diimides (cNDI) and Related Derivatives: Versatile Scaffold for Supramolecular Assembly and Functional Materials

“…Modarelli and co-workers reported bisterpyridine-functionalized cNDI derivatives (10 and 11, Figure 4) that formed extended supramolecular polymers in the presence of different divalent metal ions (Ru 2þ , Fe 2þ and Co 2þ ). 13 The typical high-emissive cNDI monomers exhibited negligible fluorescence in its metallo-supramolecular polymeric state due to electron transfer from the metal ions to the NDI moiety via the bridging ligands in the excited state. 13 George and co-workers demonstrated supramolecular polymerizations of two β-sheet forming peptide-tethered amphiphilic cNDI derivatives (12 and 13) and their pHresponsive behaviour (Figure 5).…”

“…13 The typical high-emissive cNDI monomers exhibited negligible fluorescence in its metallo-supramolecular polymeric state due to electron transfer from the metal ions to the NDI moiety via the bridging ligands in the excited state. 13 George and co-workers demonstrated supramolecular polymerizations of two β-sheet forming peptide-tethered amphiphilic cNDI derivatives (12 and 13) and their pHresponsive behaviour (Figure 5). 14 One of the cNDI building blocks (12) was symmetrically functionalized with the diethoxy groups in the aromatic core, while the other one ( 13) was unsymmetrically substituted with isopropylamine and ethoxy groups.…”

“…13 The typical high-emissive cNDI monomers exhibited negligible fluorescence in its metallo-supramolecular polymeric state due to electron transfer from the metal ions to the NDI moiety via the bridging ligands in the excited state. 13…”