Daniel Fortin

A reaction-based chromogenic and fluorescent chemodosimeter for fluoride anions

An innovative trihexylsilylacetylene-containing BODIPY dye was designed and proved to be a highly selective, sensitive, and fast chromogenic and fluorescent chemodosimeter for fluorides.

Photoproperties of the polymeric {[M(dmb)2]Y]}n materials: photoinduced intrachain energy and intermolecular electron transfers, and design of photovoltaic cells

Abstract This paper describes the structural and electronic spectroscopic properties of polymeric materials of the type {[M(dmb) 2 ]Y]} n (M = Cu, Ag; dmb = 1,8-diisocyano- p -menthane; Y = BF 4 − , NO 3 − , PF 6 − , ClO 4 − ). The replacement of Y by TCNQ (tetracyanoquinodimethane anion) leads to electrically insulating materials, which upon doping with neutral TCNQ become conducting. For M = Cu, the materials are also photoconducting where a photoinduced electron transfer from the excited CuL 4 center to the neutral TCNQ is demonstrated. Finally, photovoltaic cells have been designed.

Poly(vinyl alcohol)-Poly(ethylene glycol) Double-Network Hydrogel: A General Approach to Shape Memory and Self-Healing Functionalities.

A double-network polymer hydrogel composed of chemically cross-linked poly(ethylene glycol) (PEG) and physically cross-linked poly(vinyl alcohol) (PVA) was prepared. When the hydrogel (70 wt % of water) is subjected to freezing/thawing treatment under strain, the enhanced physical network as a result of crystallization of PVA chains can stabilize the hydrogel deformation after removal of the external force at room temperature. Subsequent disruption of the physical network of PVA by heating allows for the recovery of the initial shape of the hydrogel. Moreover, the double-network hydrogel exhibits self-healing capability stemming from the physical network of PVA by virtue of the extensive interchain hydrogen bonding between the hydroxyl side groups. This study thus demonstrates a general approach to imparting both the shape memory and self-healing properties to chemically cross-linked hydrogels that otherwise do not have such functionalities. Moreover, by making use of the fixed hydrogel elongation, the effect of anisotropy arising from chain orientation on the self-healing was also observed.

Reactivity of CuI and CuBr toward Et2S: a reinvestigation on the self-assembly of luminescent copper(I) coordination polymers.

CuI reacts with SEt(2) in hexane to afford the known strongly luminescent 1D coordination polymer [(Et(2)S)(3){Cu(4)(mu(3)-I)(4)}](n) (1). Its X-ray structure has been redetermined at 115, 235, and 275 K in order to address the behavior of the cluster-centered emission and is built upon Cu(4)(mu(3)-I)(4) cubane-like clusters as secondary building units (SBUs), which are interconnected via bridging SEt(2) ligands. However, we could not reproduce the preparation of a coordination polymer with composition [(Et(2)S)(3){Cu(4)(mu(3)-Br)(4)}](n) as reported in Inorg. Chem. 1975, 14, 1667. In contrast, the autoassembly reaction of SEt(2) with CuBr results in the formation of a novel 1D coordination polymer of composition [(Cu(3)Br(3))(SEt(2))(3)](n) (2). The crystal structure of 2 has been solved at 115, 173, 195, and 235 K. The framework of the luminescent compound 2 consists of a corrugated array with alternating Cu(mu(2)-Br)(2)Cu rhomboids, which are connected through two bridging SEt(2) ligands to a tetranuclear open-cubane Cu(4)Br(4) SBU, ligated on two external Cu atoms with one terminal SEt(2). The solid-state luminescence spectra of 1 and 2 exhibit intense halide-to-metal charge-transfer emissions centered at 565 and 550 nm, respectively, at 298 K. A correlation was also noted between the change in the full width at half-maximum of the emission band between 298 and 77 K and the relative flexibility of the bridging ligand. The emission properties of these materials are also rationalized by means of density functional theory (DFT) and time-dependent DFT calculations performed on 1.

Highly efficient iridium(III) phosphors with phenoxy- substituted ligands and their high-performance OLEDs†

Two new iridium(III) cyclometallated complexes (1 and 2) based on the 2-(1-phenoxy-4-phenyl)-5-methylpyridine ligand have been developed. By attaching a flexible phenoxy group on the phenyl ring of 2-phenylpyridine (Hppy), the light-emitting properties of the resulting IrIII complexes have been improved, while the introduction of an electron-donating methyl group on the pyridyl ring of Hppy can keep the triplet emission in the green region by compensating for the reduced energy gap caused by the phenoxy group. Owing to the unique electronic structures induced by the ligand, the vacuum-evaporated organic light-emitting devices (OLEDs) of the type [ITO/NPB (40 nm)/(1 or 2):CBP (20 nm)/BCP (10 nm)/Alq3 (30 nm)/LiF (1 nm)/Al (100 nm)] furnished peak OLED efficiencies at 10.0%, 31.1 cd A−1 and 14.5 lm W−1 for 1 and 11.7%, 38.1 cd A−1 and 31.8 lm W−1 for 2. By replacing the electron-injection/electron-transporting materials (BCP and Alq3) with TPBi, the green-emitting devices based on 1 gave outstanding peak efficiencies at 22.5%, 76.2 cd A−1 and 72.8 lm W−1. Extremely high peak efficiencies of 24.5%, 84.6 cd A−1 and 77.6 lm W−1 were even obtained for the 2-doped devices and both of them are superior in performance to the benchmark dopants Ir(ppy)3 and Ir(ppy)2(acac). Moreover, polymer light-emitting devices were also fabricated using 1 and 2via the spin-coating method, and their device performances are characterized by 14.4%, 39.5 cd A−1 and 12.4 lm W−1 for 1 and 12.6%, 29.6 cd A−1 and 18.1 lm W−1 for 2. When 2 was used to make three-color white-light OLEDs, respectable device efficiencies of 15.3 cd A−1, 7.5% and 9.1 lm W−1 were achieved and their white color CIE coordinates are improved relative to Ir(ppy)3.

Nanometer Length-Dependent Triplet-Triplet Energy Transfers in Zinc(II) Porphyrin/trans-Bis(ethynylbenzene)Platinum(II) Oligomers

The synthesis and characterization of organometallic oligomers of the type [(p-C(6)H(4))C[triple bond]CPt(P(n-Bu)(3))(2)C identical withC(p-C(6)H(4))Zn(P)](n) with the corresponding models [(C(6)H(5)C[triple bond]C)Pt(P(n-Bu)(3))(2)C[triple bond]C(p-C(6)H(4))Zn(P)(p-C(6)H(4))C[triple bond]CPt(P(n-Bu)(3))(2)(C[triple bond]CC(6)H(5))], where Zn(P) is zinc(II)-10,20-di(mesityl)- (n = 4, 9) or zinc(II)-10,20-di-n-pentyl-porphyrin (n = 3, 6, 9), are reported. The electronic spectra (absorption, excitation, emission, and transient absorption) and the photophysical properties (emission lifetimes and quantum yields) of these species in 2-methyltetrahyrofuran at 298 and 77 K are presented. Rates for triplet (T(1)) energy transfer, k(ET), from the [(p-C(6)H(4)C[triple bond]C)Pt(P(n-Bu)(3))(2)(C[triple bond]C-p-C(6)H(4))] spacer to Zn(P) vary from 2.4 x 10(4) to 1.3 x 10(6) s(-1). For the n-pentyl case, a rate dependence of oligomer size is noted as k(ET) increases with the number of units, n. This phenomenon is interpreted by the presence of an excitonic process (i.e., delocalization of the energy along the Zn(P) array).

Syntheses, Characterization, and Photophysical Properties of Conjugated Organometallic Pt-Acetylide/Zn(II) Porphyrin-Containing Oligomers

Two conjugated organometallic oligomers of the type (-C[triple bond]CPt(L)(2)C[triple bond]C(ZnP)-)(n) and model compounds [PhC[triple bond]CPt(L)(2)C[triple bond]C(ZnP)C[triple bond]CPt(L)(2)C[triple bond]CPh] with L = tri(n-butyl)-phosphine and ZnP = zinc(II)(10,20-bis(Ar)porphyrine) (Ar = mesityl (Mes; P1 and M1) or 3,4,5-trihexadecyloxyphenyl (P2 and M2)) were synthesized and characterized ((1)H and (31)P NMR, HRMS, elemental analysis, IR, GPC, and TGA). GPC indicates that P1 and P2 exhibit respectively approximately 6 and approximately 3 units with a polydispersity of 1.4. M1 was also characterized by X-ray crystallography. The Pt...Pt separation in M1 is 1.61 nm, which makes P1 approximately 9.6 nm long. The spectral measurements show that the absorption and photoluminescence spectra of M1, M2, P1, and P2 are remarkably red-shifted. For example, the low energy Q-band is observed at 677 +/- 1 nm in comparison with their precursors HC[triple bond]C(ZnP)C[triple bond]CH, L1 and L2 (Ar = mesityl (Mes; L1) or 3,4,5-trihexadecyloxyphenyl (L2)), both at 298 and 77 K, for which the Q-band is observed at 622 nm. The photophysical parameters, fluorescence lifetimes (tau(F)), and quantum yields (Phi(F)) show a slight decrease by a factor of approximately 2 (at most 3) following the trend L1 approximately L2 > M1 approximately M2 > P1 approximately P2, a trend explained by a combination of the heavy atom effect and an increase in internal conversion rate due to the increase in oligomer dimension. This small variation of the photophysical data for materials of a few nm in dimension contrasts with the larger change in tau(P), phosphorescence lifetimes of the Pt-containing unit in the (-C(6)H(4)C[triple bond]CPt(L)(2)C[triple bond]C-CC(6)H(4)(ZnP)-)(n) oligomers with n = 3, 6, and 9 reported earlier (Liu, L.; Fortin, D.; Harvey, P. D. Inorg. Chem. 2009, 48, 5891-5900). In this later case, tau(P) decreased by steps of an order of magnitude as n increased from 3 to 6 to 9. This decrease was explained by a T(1) energy transfer from the Pt unit (donor) to MP (acceptor) in combination with an excitonic process (energy delocalization). Because of the full conjugation in P1 and P2, these oligomers behave as distinct molecules, and no energy transfer occurs. These properties make these materials suitable candidates for photocell applications.

Light-healable hard hydrogels through photothermally induced melting–crystallization phase transition

A general method for preparing mechanically strong hydrogels that can undergo light-triggered healing was demonstrated. By loading a small amount of gold nanoparticles (AuNPs, 0.05 wt%) in hydrogels prepared with stearyl acrylate (SA), N,N-dimethylacrylamide (DMA) and N,N′-methylenebisacrylamide (MBA), whose strength is endowed by chemical crosslinking coexisting with crystallized hydrophobic SA side chains acting as the physical crosslinks, exposing a cut-through damage to a laser of wavelength at the surface plasmon resonance of AuNPs and subsequently turning off the light, gives rise to efficient healing of the hydrogel as a result of the reversible melting–crystallization phase transition of the hydrophobically associated SA chains. A hydrogel of this kind exhibits an unprecedented tensile strength, after repairing, of greater than 2 MPa. It also displays a light-controllable shape memory effect.

First halogen anion-bridged (MMX)(n)-type one-dimensional coordination polymer built upon d(10)-d(10) dimers.

The complex [Ag(2)(PhPPy(2))(2)(NCCH(3))(2)](ClO(4))(2) [PhPPy(2) = bis(2-pyridyl)phenylphosphine] reacts with NH(4)Cl to form an insoluble one-dimensional polymer of the type (MMX)(n), {[Ag(2)(PhPPy(2))(2)Cl](ClO(4))}(n). The binuclear unit, Ag(2)(PhPPy(2))(2)(2+), exhibits two PhPPy(2) tridentate ligands bridging the two Ag atoms in a head-to-tail fashion with C(2h) symmetry, and the Ag···Ag distance [3.0942(11) Å, X-ray] suggests argentophilic interactions. Each Ag center adopts a distorted trigonal-bipyramidal geometry, coordinated by one P atom and two pyridyl arms at the equatorial positions and interacting with one Cl ion and one Ag ion at the axial positions. The short Ag-Cl bond length [2.5791(7) Å] indicates the presence of some covalent character. The solid-state absorption bands spread all the way to 600 nm have been interpreted by means of density functional theory (DFT) and time-dependent DFT (B3LYP), and the lowest-energy excited states are assigned to metal/halide-to-pyridyl charge transfer, consistent with the d(10) electronic configuration of Ag. The calculated oscillator strengths are low because of the poor molecular orbital overlaps in the charge-transfer components. The novel material exhibits a luminescence band centered at about ∼520 nm.

Efficient parallel synthesis of macrocyclic peptidomimetics.

A new method for solid phase parallel synthesis of chemically and conformationally diverse macrocyclic peptidomimetics is reported. A key feature of the method is access to broad chemical and conformational diversity. Synthesis and mechanistic studies on the macrocyclization step are reported.