Synthesis, crystal structures, and dual donor luminescence sensitization in novel terbium tetracyanoplatinates.

A series of novel terbium tetracyanoplatinate compounds all incorporating tridentate 2,2':6'2″-terpyridine (terpy) or 4'-chloro-2,2':6'2″-terpyridine (terpy-Cl) were synthesized and used to investigate the phenomenon of dual-donor sensitization of Tb(3+). Judicious choice of the Tb(3+) salt and reaction conditions results in the isolation of {Tb(terpy)(H2O)2(NO3)Pt(CN)4}·CH3CN (1A), {Tb(terpy)(H2O)2(NO3)Pt(CN)4}·3.5H2O (1B), {Tb(terpy-Cl)(H2O)2(NO3)Pt(CN)4}·2.5H2O (2), [Tb(terpy)(H2O)2(CH3COO)2]2Pt(CN)4·4H2O (3), or [Tb2(terpy)2(H2O)2(CH3COO)5]2Pt(CN)4·7H2O (4). The compounds 1A, 1B, and 2 contain one-dimensional polymeric structures with bridging of [Tb(L)(NO3)(H2O)2](2+) (L = terpy or terpy-Cl) moieties by cis-bridging tetracyanoplatinate (TCP) anions as determined via single-crystal X-ray diffraction studies. Both 3 and 4, however, contain Tb(3+) coordinated by multiple acetate ligands and terpy, but not TCP, and are classified as zero-dimensional complex salts. Platinophilic interactions that dominate tetracyanoplatinate structural chemistry are present in the form of dimeric units in the polymeric compounds, but are totally absent in 3 and 4. The structural differences result in markedly different luminescence properties for the two classes of compounds. All of the polymeric compounds display efficient donor-acceptor intramolecular energy transfer (IET) from the terpy unit to the Tb(3+) ion. Although the TCP units are also directly coordinated to the Tb(3+) ion in the three polymers, only in 1B and 2 are the Pt···Pt interactions strong enough to provide MMLCT bands of appropriate energy to result in a dual-donor effect to the Tb(3+) sensitization. Even in these cases, TCP does not efficiently sensitize the Tb(3+), rather a broad band TCP emission results. However, terpy and acetate ligands are bonded directly to the Tb(3+) ion in 3 and 4 and provide a strong dual-donor sensitization effect as evidenced by the large QY for Tb(3+).

Synthesis, structural, and photoluminescence studies of Gd(terpy)(H2O)(NO3)2M(CN)2 (M = Au, Ag) complexes: multiple emissions from intra- and intermolecular excimers and exciplexes.

The highly luminescent bimetallic cyanide materials, Gd(terpy)(H(2)O)(NO(3))(2)M(CN)(2) (M = Au, Ag; GdAu and GdAg, respectively) are quick and easy to synthesize under ambient conditions. A characteristic feature exhibited by both solid-state compounds is an intense red emission when excited with UV light. Additionally, GdAu exhibits a broad-band green emission upon excitation in the near UV region. A combination of structural and spectroscopic results for the compounds helps explain the underlying conditions responsible for their unique properties. Single-crystal X-ray diffraction experiments expose their structural features, including the fact that they are isostructural. Crystallographic data for the representative GdAu compound (Mo K(α), λ = 0.71073 Å, T = 290 K): triclinic, space group P ̅1, a = 7.5707(3) Å, b = 10.0671(4) Å, c = 15.1260(4) Å, α = 74.923(3)°, ß = 78.151(3)°, γ = 88.401(3)°, V = 1089.04(7) Å(3), and Z = 2. Although the compounds crystallize as dimers containing M···M distances smaller than the sum of their van der Waals radii, the Au···Au (3.5054(4) Å) and/or the Ag···Ag (3.6553(5) Å) interactions are relatively weak and are not responsible for the low energy red emission. Rather, the green emission in GdAu presumably originates from the [Au(CN)(2)(-)](2) dimeric excimer, while the [Ag(CN)(2)(-)](2) dimers in GdAg do not display visible emission at either 290 or 77 K. The unusual red emission exhibited by both compounds likely originates from the formation of an excited state exciplex that involves intermolecular π-stacking of 2,2':6',2"-terpyridine ligands. The room-temperature and low-temperature steady-state photoluminescent properties, along with detailed time-dependent, lifetime, and quantum yield spectroscopic data provide evidence regarding the sources of the multiple visible emissions exhibited by these complexes.

A critical evaluation of material safety data sheets (MSDSs) for engineered nanomaterials.

Material safety data sheets (MSDSs) provide employers, employees, emergency responders, and the general public with basic information about the hazards associated with chemicals that are used in the workplace and are a part of every-day commerce. They are a primary information resource used by health, safety, and environmental professionals in communicating the hazards of chemicals and in making risk management decisions. Engineered nanomaterials represent a growing class of materials being manufactured and introduced into multiple business sectors. MSDSs were obtained from a total of 44 manufacturers using Internet search engines, and a simple ranking scheme was developed to evaluate the content of the data sheets. The MSDSs were reviewed using the ranking scheme, and categorized on the quality and completeness of information as it pertains to hazard identification, exposure controls, personal protective equipment (PPE), and toxicological information being communicated about the engineered nanomaterial. The ranking scheme used to evaluate the MSDSs for engineered nanomaterials was based on the determination that the data sheet should include information on specific physical properties, including particle size or particle size distribution, and physical form; specific toxicological and health effects; and protective measures that can be taken to control potential exposures. The first MSDSs for nanomaterials began to appear around 2006, so these were collected in the time period of 2007-2008. Comparison of MSDSs and changes over time were evaluated as MSDSs were obtained again in 2010-2011. The majority (67%) of the MSDSs obtained in 2010-2011 still provided insufficient data for communicating the potential hazards of engineered nanomaterials.

Solid-state photoluminescence sensitization of Tb3+ by novel Au2Pt2 and Au2Pt4 cyanide clusters.

The syntheses are reported for two novel Tb(3+) heterotrimetallic cyanometallates, K(2)[Tb(H(2)O)(4)(Pt(CN)(4))(2)]Au(CN)(2)·2H(2)O (1) and [Tb(C(10)N(2)H(8))(H(2)O)(4)(Pt(CN)(4))(Au(CN)(2))]·1.5C(10)N(2)H(8)·2H(2)O (2) (C(10)N(2)H(8) = 2,2'-bipyridine). Both compounds have been isolated as colorless crystals, and single-crystal X-ray diffraction has been used to investigate their structural features. Crystallographic data (MoKα, λ = 0.71073 Å, T = 290 K): 1, tetragonal, space group P4(2)/nnm, a = 11.9706(2) Å, c = 17.8224(3) Å, V = 2553.85(7) Å(3), Z = 4; 2, triclinic, space group P1, a = 10.0646(2) Å, b = 10.7649(2) Å, c = 17.6655(3) Å, α = 101.410(2)°, ß = 92.067(2)°, γ = 91.196(2)°, V = 1874.14(6) Å(3), Z = 2. For the case of 1, the structure contains Au(2)Pt(4) hexameric noble metal clusters, while 2 includes Au(2)Pt(2) tetrameric clusters. The clusters are alike in that they contain Au-Au and Au-Pt, but not Pt-Pt, metallophilic interactions. Also, the discrete clusters are directly coordinated to Tb(3+) and sensitize its emission in both solid-state compounds, 1 and 2. The Photoluminescence (PL) spectra of 1 show broad excitation bands corresponding to donor groups when monitored at the Tb(3+) ion f-f transitions, which is typical of donor/acceptor energy transfer (ET) behavior in the system. The compound also displays a broad emission band at ∼445 nm, assignable to a donor metal centered (MC) emission of the Au(2)Pt(4) clusters. The PL properties of 2 show a similar Tb(3+) emission in the visible region and a lack of donor-based emission at room temperature; however, at 77 K a weak, broad emission occurs at 400 nm, indicative of uncoordinated 2,2'-bipyridine, along with strong Tb(3+) transitions. The absolute quantum yield (QY) for the Tb(3+) emission ((5)D(4) → (7)F(J (J = 6-3))) in 1 is 16.3% with a lifetime of 616 µs when excited at 325 nm. In contrast the weak MC emission at 445 nm has a quantum yield of 0.9% with a significantly shorter lifetime of 0.61 µs. For 2 the QY value decreases to 9.3% with a slightly shorter lifetime of 562 µs. The reduced QY in 2 is considered to be a consequence of (1) the slightly increased donor-acceptor excited energy gap relative to the optimal gap suggested for Tb(3+) and (2) Tb(3+) emission quenching via a bpy ligand-to-metal charge transfer (LMCT) excited state.

Emission enhancement through dual donor sensitization: modulation of structural and spectroscopic properties in a series of europium tetracyanoplatinates.

The synthesis of three different europium tetracyanoplatinates all incorporating 2,2':6',2''-terpyridine (terpy) have been carried out in acetonitrile/water mixtures by reaction of Eu(3+) salts with terpy and potassium tetracyanoplatinate. The use of different Eu(3+) sources results in the isolation of Eu(C(15)H(11)N(3))(H(2)O)(2)(NO(3))(Pt(CN)(4)) x CH(3)CN (1), {Eu(C(15)H(11)N(3))(H(2)O)(3)}(2)(Pt(CN)(4))(3) x 2 H(2)O (2), or [Eu(C(15)H(11)N(3))(H(2)O)(2)(CH(3)COO)(2)](2)Pt(CN)(4) x 3 H(2)O (3) for the nitrate, triflate, or acetate salts, respectively. All three compounds have been prepared as colorless crystals, and single-crystal X-ray diffraction has been used to investigate their structural features. Crystallographic data (MoK alpha, lambda = 0.71073 A, T = 290 K): 1, monoclinic, space group P2(1)/c, a = 12.835(1), b = 15.239(1), c = 13.751(2) A, beta = 105.594(9) degrees, V = 2590.8(5) A(3), Z = 4; 2, triclinic, space group P1, a = 9.1802(8) A, b = 10.8008(9) A, c = 13.5437(9) A, alpha = 84.491(6) degrees, beta = 75.063(7) degrees, gamma = 79.055(7) degrees, V = 1272.4(2) A(3), Z = 1; 3, triclinic, space group P1, a = 12.110(3) A, b = 12.7273(11) A, c = 18.7054(16) A, alpha = 92.859(7) degrees, beta = 92.200(11) degrees, gamma = 118.057(10) degrees, V = 2534.8(7) A(3), Z = 2. Variation of the counteranions in these systems provides the opportunity to modify the structures and coordination environment of Eu(3+) for 1-3. Compounds 1 and 2 are both one-dimensional, polymeric compounds that contain Eu(3+) ions chelated by terpy and bridged by tetracyanoplatinate anions. 3 is a zero-dimensional complex salt in which Eu(3+) is coordinated by terpy, acetate, and water, but not tetracyanoplatinate. The structural differences result in varying sensitization phenomena for the three compounds. Compounds 1 and 2 display efficient donor-acceptor intramolecular energy transfer (IET) where dual donor species, terpyridine and tetracyanoplatinate, simultaneously enhance the acceptor Eu(3+) emission. In both compounds the donor species are directly coordinated to the acceptor ion, and hence a highly efficient dual-donor effect is exhibited for the IET mechanisms. In 3 where only the terpy ligand is directly coordinated to Eu(3+), the sensitization involves only one donor species. The Pt(CN)(4)(2-) unit in 3, which lacks direct bonding to Eu(3+), exhibits strong emission indicating the lack of cooperative enhancement of the lanthanide emission.

Fungal Fragments in Moldy Houses: A Field Study in Homes in New Orleans and Southern Ohio.

Smaller-sized fungal fragments (<1 µm) may contribute to mold-related health effects. Previous laboratory-based studies have shown that the number concentration of fungal fragments can be up to 500 times higher than that of fungal spores, but this has not yet been confirmed in a field study due to lack of suitable methodology. We have recently developed a field-compatible method for the sampling and analysis of airborne fungal fragments. The new methodology was utilized for characterizing fungal fragment exposures in mold-contaminated homes selected in New Orleans, Louisiana and Southern Ohio. Airborne fungal particles were separated into three distinct size fractions: (i) >2.25 µm (spores); (ii) 1.05-2.25 µm (mixture); and (iii) < 1.0 µm (submicrometer-sized fragments). Samples were collected in five homes in summer and winter and analyzed for (1→3)-ß-D-glucan. The total (1→3)-ß-D-glucan varied from 0.2 to 16.0 ng m(-3). The ratio of (1→3)-ß-D-glucan mass in fragment size fraction to that in spore size fraction (F/S) varied from 0.011 to 2.163. The mass ratio was higher in winter (average = 1.017) than in summer (0.227) coinciding with a lower relative humidity in the winter. Assuming a mass-based F/S-ratio=1 and the spore size = 3 µm, the corresponding number-based F/S-ratio (fragment number/spore number) would be 10(3) and 10(6), for the fragment sizes of 0.3 and 0.03 µm, respectively. These results indicate that the actual (field) contribution of fungal fragments to the overall exposure may be very high, even much greater than that estimated in our earlier laboratory-based studies.

Culturability and concentration of indoor and outdoor airborne fungi in six single-family homes.

In this study, the culturability of indoor and outdoor airborne fungi was determined through long-term sampling (24-h) using a Button Personal Inhalable Aerosol Sampler. The air samples were collected during three seasons in six Cincinnati area homes that were free from moisture damage or visible mold. Cultivation and total microscopic enumeration methods were employed for the sample analysis. The geometric means of indoor and outdoor culturable fungal concentrations were 88 and 102 colony-forming units (CFU) m(-3), respectively, with a geometric mean of the I/O ratio equal to 0.66. Overall, 26 genera of culturable fungi were recovered from the indoor and outdoor samples. For total fungal spores, the indoor and outdoor geometric means were 211 and 605 spores m(-3), respectively, with a geometric mean of I/O ratio equal to 0.32. The identification revealed 37 fungal genera from indoor and outdoor samples based on the total spore analysis. Indoor and outdoor concentrations of culturable and total fungal spores showed significant correlations (r = 0.655, p<0.0001 and r = 0.633, p<0.0001, respectively). The indoor and outdoor median viabilities of fungi were 55% and 25%, respectively, which indicates that indoor environment provides more favorable survival conditions for the aerosolized fungi. Among the seasons, the highest indoor and outdoor culturability of fungi was observed in the fall. Cladosporium had a highest median value of culturability (38% and 33% for indoor and outdoor, respectively) followed by Aspergillus/Penicillium (9% and 2%) among predominant genera of fungi. Increased culturability of fungi inside the homes may have important implications because of the potential increase in the release of allergens from viable spores and pathogenicity of viable fungi on immunocompromised individuals.

Crystal structure of bis-(1,3-di-amino-propane-κ(2) N,N')bis-[2-(4-nitro-phen-yl)acetato-κO]cadmium.

In the structure of the title compound, [Cd(C8H6NO4)2(C3H10N2)2], the Cd(II) atom is located on a center of symmetry with one independent Cd-O distance of 2.3547 (17) Šand two Cd-N distances of 2.3265 (18) and 2.3449 (19) Å. The Cd(II) atom has an overall octa-hedral coordination environment. Several types of hydrogen-bonding inter-actions are evident. Both intra- and inter-molecular inter-actions occur between the amino groups and the O atoms of the acetate group. These N-H⋯O hydrogen bonds lead to a layered structure extending parallel to the bc plane. In addition, weak inter-molecular C-H⋯O inter-actions involving the nitro groups exist, leading to the formation of a three-dimensional network structure.