Photochromism and Solid State Photoluminescence of Bi and Pb Complexes and Coordination Polymers based on N-R-4,4’-bipyridinium entities (R= O-, CH3, CH2CN,…)

Date du colloque : 06/2013</p

Photochromism and Solid State Photoluminescence of Bi and Pb Complexes and Coordination Polymers based on N-R-4,4’-bipyridinium entities (R= O-, CH3, CH2CN)

Date du colloque : 05/2013</p

Bipyridinium Ligands: Highly Luminescent Bismuth Complexes

International audienc

Photochromic and Photluminescence Properties of N-substituted-4,4’-Bipyridinium based Complexes

Date du colloque : 10/2012International audienc

Porous Coordination Polymers based on (bi)pyridinium Ligands

International audienc

N-Methyl-4,4-bipyridinium and N-Methyl-N -oxide-4,4 -bipyridinium Bismuth Complexes - Photochromism and Photoluminescence in the Solid State

Three bismuth complexes based on N-methyl-4,4-bipyridinium (hMV(+)), (hMV)[Bi(hMV)Cl-5] (1), and N-methyl-N-oxide-4,4-bipyridinium (MVO+), [Bi(MVO)X-4(dmso)]center dot dmso [X = Cl (2), Br (3)], are reported. All three compounds show luminescence in the solid state with maxima at 545 nm (yellow for 1) and 560 nm (orange for 2 and 3) with quantum yields up to 10 %. Upon UV irradiation, 1 undergoes a color change from white to blue accompanied by a reduction of the photoluminescence intensity. The analysis of the crystal structure of the three complexes points to a photoinduced charge-transfer (PICT) process at the origin of the photochromism in 1

When Both Transmitting and Receiving Energies Matter: An Application of Network Coding in Wireless Body Area Networks

A network coding scheme for practical implementations of wireless body area networks is presented, with the objective of providing reliability under low-energy constraints. We propose a simple network layer protocol for star networks, adapting redundancy based on both transmission and reception energies for data and control packets, as well as channel conditions. Our numerical results show that even for small networks, the amount of energy reduction achievable can range from 29% to 87%, as the receiving energy per control packet increases from equal to much larger than the transmitting energy per data packet. The achievable gains increase as a) more nodes are added to the network, and/or b) the channels seen by different sensor nodes become more asymmetric.Comment: 10 pages, 7 figures, submitted to the NC-Pro Workshop at IFIP Networking Conference 2011, and to appear in the conference proceedings, published by Springer-Verlag, in the Lecture Notes in Computer Science (LNCS) serie

Bismuth-Based Coordination Polymers with Efficient Aggregation-Induced Phosphorescence and Reversible Mechanochromic Luminescence

Two bismuth coordination polymers (CPs), (TBA)[BiBr4(bp4mo)] (TBA=tetrabutylammonium) and [BiBr3(bp4mo)2], which are based on the rarely used simple ditopic ligand N-oxide-4,4′-bipyridine (bp4mo), show mechanochromic luminescence (MCL). High solid-state phosphorescence quantum yields of up to 85 % were determined for (TBA)[BiBr4(bp4mo)] (λem=540 nm). Thorough investigations of the luminescence properties combined with DFT and TDDFT calculations revealed that the emission is due to aggregation-induced phosphorescence (AIP). Upon grinding, both samples became amorphous, and their luminescence changed from yellow to orange and red, respectively. Heating or exposure to water vapor led to the recovery of the initial luminescence. These materials are the first examples of mechanochromic phosphors based on bismuth(III)

Aggregation induced phosphorescent N-oxyde-2,2′-bipyridine bismuth complexes and polymorphism-dependent emission

Unprecedented bismuth complexes, based on the rarely used ditopic ligand N-oxide-2,2′-bipyridine (bp2mo), crystallizing as three polymorphs, α- (1), β- (2) and γ-[BiBr3(bp2mo)2] (3), exhibit phosphorescence with a quantum yield up to 17% for the crystal phase (1), while the complex displays a weak fluorescence in solution. A study of the luminescence properties combined with DFT/TDDFT calculations reveals that the lighting phenomenon originated by aggregation induced phosphorescence correlated with the weak intermolecular interactions present in the different crystal phases

The motley family of polar compounds (MV) M(X5-xX (x)) based on anionic chains of trans-connected M-(III)(X,X)(6) octahedra (M=Bi, Sb; X, X=Cl, Br, I) and methylviologen (MV) dications

The search for hybrid organic-inorganic materials remains a great challenge in the field of ferroelectrics. Following the discovery of the room temperature ferroelectric material (MV)[BiI3Cl2] (MV2+: methyl-viologen) exhibiting the highest polarization value in the field of hybrid ferroelectrics, we report here nine new hybrids with the general formulation (MV)[(MX5-xX)-X-(III)(x)] (M=Bi, Sb; X, X=CI, Br, I): (MV)[BiCl3.3Br1.7] (1), (MV)[BiCl1.3Br3.7] (2), (MV)[BiBr3.2I1.8] (3), (MV)[SbCl5] (4), (MV)[SbBr5] (5), (MV)[SbCl3.8Br1.2] (6). (MV)[SbCl2.4Br2.6] (7), (MV)[SbI3Cl2] (8) and (MV)[SbBr3.8I1.2] (9). Depending on the presence of polar chains or not, and on the coupling of polar chains, two types of centrosymmetrical structures [C1] and [C2] and two types of polar structures [P1] and [P2] are defined. (2) undergoes a paraelectric-to-relaxor ferroelectric transition around 100-150 K depending of the frequency showing that the Curie temperature, T-C, of (MV)[BiBr5] (243 K) can be modulated by the substitution of Br by Cl. The most interesting family is the [P2] type because the syn coupling of polar chains is in favor of high polarization values, as in (MV)[BiI3Cl2]. Five of the nine new hybrids, (4), (6-9), which have the [P2] type structure are potential ferroelectrics. (C) 2012 Elsevier Inc. All rights reserved