A pinboard by
Amie Norton

Graduate Student studying Vapochromic materials that respond to VOCs (Volatile Organic Compounds)


Vapochromic complexes have attracted much attention due to their potential use as visual indicators for hazardous chemicals such as VOC (Volatile Organic Compounds). The biggest hazard is that many VOCs cause cancers. In particular, platinum(II) salts are intriguing because their solid-state color and luminescence are strongly dependent on Pt…Pt separations.


Development of Ion-Conductive and Vapoluminescent Porous Coordination Polymers Composed of Ruthenium(II) Metalloligand.

Abstract: We synthesized two new porous coordination polymers (PCPs) {Ln7(OH)5[Ru(dcbpy)3]4·4nH2O} (Ln7-Ru4; Ln = Ce, Nd) composed of the luminescent ruthenium(II) metalloligand [Ru(4,4'-dcbpy)3](4-) ([4Ru]; 4,4'-dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and lanthanide ions Ln(3+) (Ln = Ce, Nd). These two PCPs Ln7-Ru4 are isomorphous with the previously reported PCP La7-Ru4, and the lattice constants (a, c, and unit cell volume V) changed systematically according to the lanthanide contraction. All three Ln7-Ru4 compounds have OH(-) anion containing porous structures and a large number of hydrate water molecules within the pores, resulting in moderate ion conductivities (10(-6)-10(-7) S cm(-1)) at 90% relative humidity (RH) and 298 K. In contrast, the structural transformation of Ln7-Ru4 associated with water-vapor adsorption/desorption strongly depends on the lanthanide ion; the Ln7-Ru4 compounds with larger Ln(3+) ions recover the original porous structure at lower relative humidities (RH). A similar trend was observed for the ion conduction activation energy, suggesting that the bridging Ln(3+) ion plays an important role in the formation of the ion-conductive pathways. La7-Ru4 and Ce7-Ru4 exhibit vapochromic luminescence associated with water vapor adsorption/desorption, arising from the (3)MLCT emission of [4Ru]. This vapochromic behavior is also affected by the replacement of the Ln(3+) ion; the vapochromic shift of Ce7-Ru4 was observed at RH values (near 100% RH) higher than that of La7-Ru4. (3)MLCT emissions of the [4Ru] metalloligand in Nd7-Ru4 were barely observable in the visible region, but sharp emission bands characteristic of 4f-4f transitions of the Nd(3+) ion were observed in the near-infrared (NIR) region (arising from the (1)MLCT transition of [4Ru]), suggesting the transfer of energy from the [4Ru] (3)MLCT excited state to the 4f-4f transition state of the Nd(3+) ions.

Pub.: 18 Feb '17, Pinned: 29 Jun '17

Excimer-Monomer Photoluminescence Mechanochromism and Vapochromism of Pentiptycene-Containing Cyclometalated Platinum(II) Complexes.

Abstract: The ability of the bulky H-shaped pentiptycene scaffold in promoting the mechanochromic and vapochromic luminescence properties for organometallic materials has been demonstrated with the N^C^N cyclometalated platinum(II) complexes [X-NCNPtY], where X = Br or Pa, the substituent on the terdentate dipyridylbenzene N^C^N ligand, and Y = Cl or Pa, the ancillary ligand, in which Pa = pentiptycene acetylene. Intermolecular interactions between the planar NCNPt cores are described by π-π and d-π interactions with negligible Pt(II)···Pt(II) bonding, corresponding to ligand-centered excimer rather than metal-metal-to-ligand charge-transfer emission, for these platinum(II) complexes in aggregates and in the solid state. Interplay of the relative excimer-to-monomer emission intensity in response to external force and/or vapor stimuli accounts for the luminescence mechanochromism and vapochromism of the pentiptycene-incorporated platinum(II) complexes [Pa-NCNPtCl], [Br-NCNPtPa], and [Pa-NCNPtPa], whereas the pentiptycene-free counterpart [Br-NCNPtCl] undergoes little or no emission color response. In particular, the complex [Pa-NCNPtCl] displays a distinct response to aromatic versus nonaromatic organic vapors: namely, aromatic vapors such as benzene convert the excimer emission to monomer emission, but the opposite is true with nonaromatic vapors. A two-stage emission color change from red to orange and then to yellow could thus be achieved by grinding and by subsequent benzene-vapor fuming. Another feature associated with [Pa-NCNPtCl] is an aggregation-induced green → magenta luminescence color change in water/tetrahydrofuran mixed solutions. The structure-luminescence property relationship is discussed in relation to intermolecular interactions and packing modes that depend on the number and positions of pentiptycene groups.

Pub.: 14 Apr '17, Pinned: 29 Jun '17

Copper(II) Dihalotetracyanoplatinate(IV) Coordination Polymers and Their Vapochromic Behavior

Abstract: The two coordination polymers [Cu(H2O)2(μ2-NC)4PtX2] (X = Cl, Br) were synthesized, structurally characterized, and tested for vapochromic response to selected N- and O-donor analytes, of which the bromine-containing materials in particular show large colorimetric changes. Both the parent and analyte adduct materials form 2-D coordination polymer networks that align through X···X interactions. New Pt(IV) materials with [PtBr(NH3)(CN)4]− and [PtCl(OH)(CN)4]2− linkers are also described.The coordination polymers [Cu(H2O)2(μ2-NC)4PtX2] (X = Cl, Br) form networks of square grid sheets that align in a staggered manner with one another via weak X···X interactions. Upon stepwise dehydration, the layers fuse, forming a 3-D network of distorted cubes. The materials were tested for visible vapochromic, Raman, and IR response to dimethyl sulfoxide, N,N-dimethylformamide, and pyridine. Analyte-bound coordination polymers of the form Cu(analyte)2[PtX2(CN)4] were structurally characterized by PXRD and found to form layers of square grids that align through X···X interactions. The reaction of [Cu(H2O)2(μ2-NC)4PtX2] with concentrated aqueous NH3 generated [PtBr(CN)4(NH3)]− and [PtCl(CN)4(OH)]2– anions that were incorporated into 1-D chain structures. UV–visible reflectance data show that a combination of shifting d–d transitions and the visible Br–Pt LMCT absorption band in [Cu(H2O)2(μ2-NC)4PtBr2] results in a greater vapochromic effect in comparison to that in chlorine-containing analogues.

Pub.: 27 Jun '17, Pinned: 29 Jun '17