Irreversible Solvatochromic Zn-Nanopaper Based on Zn(II) Terpyridine Assembly and Oxidized Nanofibrillated Cellulose

A new irreversible solvatochromic Zn-nanopaper has been produced through the coordination-driven assembly of Zn­(II)-terpyridine complex (Zn-tpy) on the surface of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (tCNF). The Zn-tpy as a photoactive center exhibits a changed emission color from greenish-blue to yellow after coordination with the carboxylate anion on the surface of tCNF. Theoretic calculations support that the longer wavelength emission is the result of a metal–ligand charge transfer. When exposed to solvents and then dried, the coordination bond between the Zn-tpy and tCNF experienced a dynamic, reversible process, where the lowest-energy excited state emitted by the Zn-tpy was “inverted”, which is a typical phenomenon of irreversible solvatochromism. The shifts of the emission colors of the Zn-nanopaper appeared result from its exposure to specific solvents and occurred in a matter of minutes. After solvent exposure, it was found that the emission colors of the nanopaper are not recovered to its original state. The different emissive Zn-nanopapers are easily prepared by post-processing using a solvatochromic process. This highly transparent Zn-nanopaper with post-processable emission offers unprecedented potential applications in the areas of memory devices, fluorescent switches, and organic light-emitting diodes (OLEDs)

Irreversible Solvatochromic Zn-Nanopaper Based on Zn(II) Terpyridine Assembly and Oxidized Nanofibrillated Cellulose

A new irreversible solvatochromic Zn-nanopaper has been produced through the coordination-driven assembly of Zn­(II)-terpyridine complex (Zn-tpy) on the surface of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (tCNF). The Zn-tpy as a photoactive center exhibits a changed emission color from greenish-blue to yellow after coordination with the carboxylate anion on the surface of tCNF. Theoretic calculations support that the longer wavelength emission is the result of a metal–ligand charge transfer. When exposed to solvents and then dried, the coordination bond between the Zn-tpy and tCNF experienced a dynamic, reversible process, where the lowest-energy excited state emitted by the Zn-tpy was “inverted”, which is a typical phenomenon of irreversible solvatochromism. The shifts of the emission colors of the Zn-nanopaper appeared result from its exposure to specific solvents and occurred in a matter of minutes. After solvent exposure, it was found that the emission colors of the nanopaper are not recovered to its original state. The different emissive Zn-nanopapers are easily prepared by post-processing using a solvatochromic process. This highly transparent Zn-nanopaper with post-processable emission offers unprecedented potential applications in the areas of memory devices, fluorescent switches, and organic light-emitting diodes (OLEDs)

Near-Infrared Luminescent PMMA-Supported Metallopolymers Based on Zn–Nd Schiff-Base Complexes

On the basis of self-assembly from the divinylphenyl-modified Salen-type Schiff-base ligands <b>H</b>_<b>2</b><b>L</b>^<b>1</b> (<i>N</i>,<i>N</i>′-bis­(5-(3′-vinylphenyl)-3-methoxy-salicylidene)­ethylene-1,2-diamine) or <b>H</b>_<b>2</b><b>L</b>^<b>2</b> (<i>N</i>,<i>N</i>′-bis­(5-(3′-vinylphenyl)-3-methoxy-salicylidene)­phenylene-1,2-diamine) with Zn­(OAc)₂·2H₂O and Ln­(NO₃)₃·6H₂O in the presence of pyridine (Py), two series of heterobinuclear Zn–Ln complexes [Zn­(L^<i>n</i>)­(Py)­Ln­(NO₃)₃] (<i>n</i> = 1, Ln = La, <b>1</b>; Ln = Nd, <b>2</b>; or Ln = Gd, <b>3</b> and <i>n</i> = 2, Ln = La, <b>4</b>; Ln = Nd, <b>5</b>; or Ln = Gd, <b>6</b>) are obtained, respectively. Further, through the physical doping and the controlled copolymerization with methyl methacrylate (MMA), two kinds of PMMA-supported hybrid materials, doped <b>PMMA/[Zn­(L</b>^{<b><i>n</i></b>}<b>)­(Py)­Ln­(NO</b>_<b>3</b><b>)</b>_<b>3</b><b>]</b> and Wolf Type II Zn²⁺–Ln³⁺-containing metallopolymers <b>Poly­(MMA-<i>co</i>-[Zn­(L</b>^{<b><i>n</i></b>}<b>)­(Py)­Ln­(NO</b>_<b>3</b><b>)</b>_<b>3</b><b>])</b>, are obtained, respectively. The result of their solid photophysical properties shows the strong and characteristic near-infrared (NIR) luminescent Nd³⁺-centered emissions for both <b>PMMA/[Zn­(L</b>^{<b><i>n</i></b>}<b>)­(Py)­Nd­(NO</b>_<b>3</b><b>)</b>_<b>3</b><b>]</b> and <b>Poly­(MMA-<i>co</i>-[Zn­(L</b>^{<b><i>n</i></b>}<b>)­(Py)­Nd­(NO</b>_<b>3</b><b>)</b>_<b>3</b><b>])</b>, where ethylene-linked hybrid materials endow relatively higher intrinsic quantum yields due to the sensitization from both ¹LC and ³LC of the chromorphore than those from only ¹LC in phenylene-linked hybrid materials, and the concentration self-quenching of Nd³⁺-based NIR luminescence could be effectively prevented for the copolymerized hybrid materials in comparison with the doped hybrid materials

Anion-Induced Self-Assembly of Luminescent and Magnetic Homoleptic Cyclic Tetranuclear Ln₄(Salen)₄ and Ln₄(Salen)₂ Complexes (Ln = Nd, Yb, Er, or Gd)

Unique homoleptic cyclic tetranuclear Ln₄(Salen)₄ complexes [Ln₄(L)₂(HL)₂(μ₃-OH)₂Cl₂]·2Cl (Ln = Nd, <b>1</b>; Ln = Yb, <b>2</b>; Ln = Er, <b>3</b>; Ln = Gd, <b>4</b>) or Ln₄(Salen)₂ complexes [Ln₄(L)₂(μ₃-OH)₂(OAc)₆] (Ln = Nd, <b>5</b>; Ln = Yb, <b>6</b>; Ln = Er, <b>7</b>; Ln = Gd, <b>8</b>) have been self-assembled from the reaction of the hexadentate Salen-type Schiff-base ligand <b>H</b>_<b>2</b><b>L</b> with LnCl₃·6H₂O or Ln­(OAc)₆·6H₂O (Ln = Nd, Yb, Er, or Gd), respectively (<b>H</b>_<b>2</b><b>L</b>: <i>N</i>,<i>N</i>′-bis­(salicylidene)­cyclohexane-1,2-diamine). The result of their photophysical properties shows that the strong and characteristic NIR luminescence for complexes <b>1</b>–<b>2</b> and <b>5</b>–<b>6</b> with emissive lifetimes in microsecond ranges are observed, and the sensitization arises from the excited state (both ¹LC and ³LC) of the hexadentate Salen-type Schiff-base ligand with the flexible linker. Temperature dependence (1.8–300 K) magnetic susceptibility studies of the eight complexes suggest the presence of an antiferromagnetic interaction between the Ln³⁺ ions