Ultralong Persistent Room Temperature Phosphorescence of Metal Coordination Polymers Exhibiting Reversible pH-Responsive Emission

Ultra-long-persistent room temperature phosphorescence (RTP) materials have attracted much attention and present various applications in illumination, displays, and the bioimaging field; however, the persistent RTP is generally from the inorganic phosphor materials to date. Herein, we show that the metal coordination polymers (CPs) could be new types of emerging long-lived RTP materials for potential sensor applications. First, two kinds of Cd-based CPs, Cd­(<i>m</i>-BDC)­(H₂O) (<b>1</b>) and Cd­(<i>m</i>-BDC)­(BIM) (<b>2</b>) (<i>m</i>-BDC = 1,3-benzenedicarboxylic acid; BIM = benzimidazole), were obtained through a hydrothermal process, and the samples were found to exhibit two-dimensional layered structures, which are stabilized by interlayer C–H···π interaction and π···π interaction, respectively. The CPs show unexpected second-time-scale ultra-long-persistent RTP after the removal of UV excitation, and this persistent emission can be detected easily on a time scale of 0–10 s. The CPs also feature a tunable luminescence decay lifetime by adjusting their coordination situation and packing fashion of ligands. Theoretical calculation further indicates that the introduction of the second ligand could highly influence the electronic structure and intermolecular electron transfer toward tailoring the RTP of the CP materials. Moreover, CP <b>2</b> exhibits well-defined pH- and temperature-dependent phosphorescence responses. Therefore, this work provides a facile way to develop new type of CPs with steady-state and dynamic tuning of the RTP properties from both experimental and theoretical perspectives, which have potential applications in the areas of displays, pH/temperature sensors, and phosphorescence logic gates. On account of suitable incorporation of inorganic and organic building blocks, it can be expected that the ultra-long-persistent RTP CPs can be extended to other similar systems due to the highly tunable structures and facile synthesis routes

A β-d-Allopyranoside-Grafted Ru(II) Complex: Synthesis and Acid−Base and DNA-Binding Properties

A new ruthenium(II) complex grafted with β-d-allopyranoside, Ru(bpy)2(Happip)(ClO4)2 (where bpy = 2,2′-bipyridine; Happip = 2-(4-(β-d-allopyranoside)phenyl)imidazo[4,5-f][1,10]phenanthroline), has been synthesized and characterized by elemental analysis, 1H NMR spectroscopy, and mass spectrometry. The acid−base properties of the complex have been studied by UV−visible and luminescence spectrophotometric pH titrations, and ground- and excited-state ionization constants have been derived. The Ru(II) complex functions as a DNA intercalator as revealed by UV−visible and emission titrations, salt effects, steady-state emission quenching by [Fe(CN)6]4−, DNA competitive binding with ethidium bromide, DNA melting experiment, and viscosity measurements

Layer-by-Layer Assembly of Graphene Oxide and a Ru(II) Complex and Significant Photocurrent Generation Properties

The multilayer films were fabricated by layer-by-layer electrostatically coassembling graphene oxide and a ruthenium complex of [Ru­(bpy)₂L]­(ClO₄)₂ {L = 2-(2,6-di­(pyridin-2-yl)­pyridine-4-yl)-1<i>H</i>-imidazo­[4,5-<i>f</i>]-1,10-phenanthroline} and characterized using UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and cyclic voltammetry. The dependence of redox properties and cathodic photocurrents on the number of layers deposited and the photocurrent generation mechanism and polarity were studied in detail. The homogeneous growth and close packing of the two film-forming components, linear relationships of the dark cyclic voltometry peak currents and photocurrents vs number of layers deposited, and large cathodic photocurrent density of 4.1 μA/cm² for a four-layer film make this novel hybrid thin film promising applications ranging from molecular photovoltaic and photocatalytic molecular devices to photoelectrochemical sensing

Molecular Light Switches for Calf Thymus DNA Based on Three Ru(II) Bipyridyl Complexes with Variations of Heteroatoms

The three Ru(II) complexes of [Ru(bpy)2(bipp)](ClO4)2 (1), [Ru(bpy)2(bopp)](ClO4)2 (2), and [Ru(bpy)2(btpp)](ClO4)2 (3) (where bpy = 2,2‘-bipyridine, bipp = 2-benzimidazoyl-pyrazino[2,3-f] [1,10]phenanthroline, bopp = 2-benzoxazolyl-pyrazino[2,3-f] [1,10]phenanthroline, and btpp = 2-benzthiazolyl-pyrazino[2,3-f] [1,10]phenanthroline) with variations in heteroatoms of NH (1), O(2), and S(3), have been synthesized and characterized. These complexes have been shown to act as promising calf thymus DNA intercalators and a new class of DNA light switches for the DNA, as evidenced by UV−visible and luminescence titrations, steady-state emission quenching by [Fe(CN)6]4-, DNA competitive binding with ethidium bromide, reverse salt titrations, viscosity measurements, and DNA melting experiments

Highly Sensitive and Selective Difunctional Ruthenium(II) Complex-Based Chemosensor for Dihydrogen Phosphate Anion and Ferrous Cation

The anion-interaction properties of a Ru­(II) complex of [Ru­(bpy)₂(Htppip)]­(ClO₄)₂·H₂O·DMF (<b>RuL</b>) {bpy =2,2′-bipyridine and Htppip =2-(4-(2,6-di­(pyridin-2-yl)­pyridin-4-yl)­phenyl)-1<i>H</i>-imidazo­[4,5-<i>f</i>]­[1,10]­phenanthroline} were thoroughly investigated in CH₃CN and CH₃CN/H₂O (50:1, v/v) solutions by UV–visible absorption, emission, and ¹H NMR spectra. These analyses revealed that <b>RuL</b> acts as an efficient “turn on” emission sensor for H₂PO₄^–, and a “turn off” sensor for F^– and OAc^–; in addition, <b>RuL</b> exhibited slightly disturbed emission spectra in the presence of the other anions studied (Cl^–, Br^–, I^–, NO₃^–, and ClO₄^–). The cation-sensing properties of <b>RuL</b> were also studied in both neat CH₃CN and aqueous 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer (pH = 7.2)/CH₃CN (71/1, v/v) solutions. <b>RuL</b> was found to exhibit a colorimetric sensing ability that was highly selective for Fe²⁺, as evidenced by an obvious color change from pale yellow to light red-purple to the naked eye over the other cations studied (Na⁺, Mg²⁺, Ba²⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Ag⁺). To obtain insights into the possible binding modes and the sensing mechanisms, ¹H NMR spectral analysis, luminescence lifetime measurements, and density functional theoretical calculations were also performed

Molecular Light Switches for Calf Thymus DNA Based on Three Ru(II) Bipyridyl Complexes with Variations of Heteroatoms

The three Ru(II) complexes of [Ru(bpy)2(bipp)](ClO4)2 (1), [Ru(bpy)2(bopp)](ClO4)2 (2), and [Ru(bpy)2(btpp)](ClO4)2 (3) (where bpy = 2,2‘-bipyridine, bipp = 2-benzimidazoyl-pyrazino[2,3-f] [1,10]phenanthroline, bopp = 2-benzoxazolyl-pyrazino[2,3-f] [1,10]phenanthroline, and btpp = 2-benzthiazolyl-pyrazino[2,3-f] [1,10]phenanthroline) with variations in heteroatoms of NH (1), O(2), and S(3), have been synthesized and characterized. These complexes have been shown to act as promising calf thymus DNA intercalators and a new class of DNA light switches for the DNA, as evidenced by UV−visible and luminescence titrations, steady-state emission quenching by [Fe(CN)6]4-, DNA competitive binding with ethidium bromide, reverse salt titrations, viscosity measurements, and DNA melting experiments

Synthesis, Characterization, and Second-Harmonic Generation Studies of Surfactant Rhenium(I) Diimine Complexes in Langmuir−Blodgett Films. X-ray Crystal Structure of <i>fac</i>-ClRe(CO)₃L (L = 9-Heptylamino-4,5-diazafluorene)

A series of surfactant complexes of general formula, fac-ClRe(CO)3L (L = 9-octadecylamino-4,5-diazafluorene, 9-(4‘-hexadecylanilino)-4,5-diazafluorene, N-(4‘-hexadecylphenyl)pyridine-2-carbaldimine, and 9-heptylamino-4,5-diazafluorene), were synthesized and characterized by elemental analyses and 1H NMR, UV−vis, IR, and luminescence spectroscopy. The complex fac-ClRe(CO)3L (L = 9-heptylamino-4,5-diazafluorene) was structurally characterized. The formation and optical properties of their Langmuir−Blodgett (LB) films were studied by surface pressure−area (π−A) isotherms and UV−vis and luminescence spectroscopy, and the second-harmonic generation (SHG) behavior was also investigated

Synthesis and Optical and Electroluminscent Properties of Two New Solution-Processable N∩O^- Re(I) Complexes

Two ReI complexes of Re2(CO)6(TOB)2 and Re(CO)3(TOB)(py) (where TOB = deprotonated 2-(2H-benzo[d] [1,2,3]triazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, py = pyridine) have been synthesized and characterized by 1H NMR, elemental analysis, FT-IR, UV−vis, and emission spectroscopy, and cyclic voltammetry. The dimeric Re2(CO)6(TOB)2 is found to undergo dissociative solvolysis to form monomeric Re(CO)3(TOB)(solv) in coordinating media, and the solvolysis rate constants in acetonitrile, dimethyl sulfoxide, pyridine, and N,N-dimethylformamide are derived. A Re2(CO)6(TOB)2-containing electroluminescent device of ITO/poly(3,4-ethylenedioxythiophene) (50 nm)/poly(N-vinylcarbazole):Re2(CO)6(TOB)2 (5:1, w/w) (70 nm)/LiF(0.5 nm)/Al (150 nm) emits yellow light with a turn-on voltage of ∼7.0 V, a maximum luminance of 96 cd/m2 at a bias voltage of 20 V, and a maximum power efficiency of 0.029 lm/W at a luminance of 12 cd/m2, while for a Re(CO)3(TOB)(py)-containing device of ITO/poly(3,4-ethylenedioxythiophene) (50 nm)/poly(N-vinylcarbazole):Re(CO)3(TOB)(py) (5:1, w/w) (70 nm)/LiF(0.5 nm)/Al (150 nm), a low turn-on voltage of 2.3 V, a maximum luminance of 75 cd/m2 at a bias voltage of 5.1 V, and a high maximum power efficiency of 9.0 lm/W at a luminance of 20 cd/m2 are achieved

A Triphenylamine-Grafted Imidazo[4,5-<i>f</i>][1,10]phenanthroline Ruthenium(II) Complex: Acid−Base and Photoelectric Properties

A new heteroleptic ruthenium(II) complex of [Ru(Hipdpa)(Hdcbpy)(NCS)2]−·0.5H+·0.5[N(C4H9)4]+ Ru(Hipdpa) {where Hdcbpy = monodeprotonated 4,4′-dicarboxy-2,2′-bipyridine and Hipdpa = 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-N,N-diphenylaniline} was synthesized and characterized by elementary analysis, standard spectroscopy techniques, and cyclic voltammetry. The ground- and excited-state acid−base properties of Ru(Hipdpa) were studied by means of UV−vis absorption spectrophotometric and spectrofluorimetric titrations in 4:1(v/v) Britton-Robinson/dimethylformamide buffer solution. The four-step separate protonation/deprotonation processes were found in the ground states, and one of which taking place near the physiological pH range. The two observable excited-state protonation/deprotonation processes were found for the Ru(Hipdpa), constituting pH-induced “off−on−off” emission switches. The performance of the complexes as photosensitizers in nanocrystalline TiO2-based liquid solar cells containing an electrolyte solution (0.05 M I2, 0.5 M LiI, and 0.5 M 4-tert-butylpyridine in 50% acetonitrile and 50% propylene carbonate) was investigated and found to achieve a much improved device performance (a short-circuit photocurrent density of 18.7 mA cm−2, an open-circuit voltage of 630 mV, and an overall conversion efficiency of 6.85%) compared to a triphenylamine-free parent complex [Ru(Hpip)(Hdcbpy)(NCS)2]−·[N(C4H9)4]+-based device {Hpip = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline} and a comparable performance to that of cis-bis(isothiocyanato)bis(2,2′-bipyridine-4,4′-dicarboxylic acid)ruthenium(II) (N3) under identical experimental conditions. A density functional theory calculation of the molecular structures and electronic properties of the complexes was also carried out in an effort to understand their effectiveness in TiO2-based solar cells