Expanding Luminescence Horizons in Macropolyhedral Heteroboranes.

Luminescence is observed in three novel macropolyhedral nineteen- and eighteen-vertex chalcogenaboranes: Se2B17H17 (1), SeB17H19 (3) and SeB18H20 (4). This led us to the recognition that previously published macropolyhedral heteroborane species might also exhibit luminescence. Thus, the known nineteen- and eighteen-vertex dithiaboranes S2B17H17 (2), n-S2B16H16 (5) and i-S2B16H16 (6) were synthesised and also found to exhibit a range of luminescent properties. These macropolyhedral species are very different from the previously unique fluorescent binary borane B18H22 in terms of their structural architectures, by the presence of borane cluster hetero atoms, and, as in the cases of 5 and 6, that their synthetic origins are not derived simply through the modification of B18H22 itself. They consequently greatly expand the possibilities of finding new luminescent inorganic borane species.

Simple Route to [PSH][B9H14] and a Contemporary Study of Its Solid-State Dynamic Behavior.

The 1,8-bis(dimethylamino)naphthalenium ([PSH]+) decaborane salt, [PSH][B10H13], has been found to react in ethanol to form [PSH][B9H14] (1), affording a simple route to the synthesis of the arachno-nonaborate anion. This new polyhedral salt is characterized by NMR spectroscopy and X-ray diffraction. The measurement of diffusion coefficients by NMR methods demonstrates that the [PSH]+ cation and the [B9H14]- anion form ion pairs in a non-coordinating solvent such as CH2Cl2, whereas in CD3CN the formation of ion pairs was not observed. Insights into the long-known low-energy dynamic behavior, which involves the bridging and endo-terminal hydrogen atoms, are elucidated using DFT calculations. Salts [PSH][B9H14] (1) and [PSH][B9H14]·0.5CHCl3 (solvated, 1·0.5CHCl3) have also been studied by X-ray diffraction analysis. A solid-state NMR study has demonstrated that K[B9H14] and [PSH][B9H14] (1) undergo significantly different motion regimes, being a low-energy, weakly temperature-dependent process for 1, which may be ascribed to some type of low-amplitude reorientation of the whole boron cages. This process may be the mechanism for the low- to-room-temperature order-disorder hidden transition found by X-ray analysis.

A Window into the Workings of anti-B18H22 Luminescence-Blue-Fluorescent Isomeric Pair 3,3'-Cl2-B18H20 and 3,4'-Cl2-B18H20 (and Others).

The action of AlCl3 on room-temperature tetrachloromethane solutions of anti-B18H22 (1) results in a mixture of fluorescent isomers, 3,3'-Cl2-B18H20 (2) and 3,4'-Cl2-B18H20 (3), together isolated in a 76% yield. Compounds 2 and 3 are capable of the stable emission of blue light under UV-excitation. In addition, small amounts of other dichlorinated isomers, 4,4'-Cl2-B18H20 (4), 3,1'-Cl2-B18H20 (5), and 7,3'-Cl2-B18H20 (6) were isolated, along with blue-fluorescent monochlorinated derivatives, 3-Cl-B18H21 (7) and 4-Cl-B18H21 (8), and trichlorinated species 3,4,3'-Cl3-B18H19 (9) and 3,4,4'-Cl3-B18H19 (10). The molecular structures of these new chlorinated derivatives of octadecaborane are delineated, and the photophysics of some of these species are discussed in the context of the influence that chlorination bears on the luminescence of anti-B18H22. In particular, this study produces important information on the effect that the cluster position of these substitutions has on luminescence quantum yields and excited-state lifetimes.

"Activated Borane" - A Porous Borane Cluster Network as an Effective Adsorbent for Removing Organic Pollutants.

The unprecedented co-thermolysis of decaborane(14) (nido-B10 H14 ) and toluene results in a novel porous material (that we have named "activated borane") containing micropores between 1.0 and 1.5 nm in diameter and a specific surface area of 774 m2 g-1 (Ar, 87 K) that is thermally stable up to 1000 °C. Solid state 1 H, 11 B and 13 C MAS NMR, UV-vis and IR spectroscopies suggest an amorphous structure of borane clusters interconnected by toluene moieties in a ratio of about three toluene molecules for every borane cluster. In addition, the structure contains Lewis-acidic tri-coordinated boron sites giving it some unique properties. Activated borane displays high sorption capacity for pollutants such as sulfamethoxazole, tramadol, diclofenac and bisphenol A that exceed the capacity of commercially-available activated carbon. The consistency in properties for each batch made, and the ease of its synthesis, make activated borane a promising porous material worthy of broad attention.

Direct Phenylation of nido-B10H14.

As a preliminary step toward its condensation into the porous polymer Activated Borane, the thermolysis of nido-B10H14 (1) in benzene at 200 °C results in the generation of a number of phenylated borane molecular species. The principal product is the new monophenylated compound 5-Ph-nido-B10H13 (2), isolated in 48% yield (based on consumption of 1) and structurally characterized by single-crystal X-ray diffraction analysis, NMR, and mass spectrometry along with other minor products, such as 6-Ph-nido-B10H13 (3), for which we observe UV-light-driven conversion into 2 via a "vertex-flip" mechanism, and novel diphenylated 5,8-Ph2-nido-B10H12 (4). Together, the phenylated derivatives provide a valuable insight into the assembly of Activated Borane and ultimately inform on its structure. The new compounds also display strong blue fluorescence in both solid-state and in solution and are the first examples of the direct phenylation of nido-B10H14, thus opening the door to the straight-forward synthesis of highly luminescent organic-borane hybrid systems.

Macropolyhedral Chalcogenaboranes: Insertion of Selenium into the Isomers of B18H22.

High yields of novel macropolyhedral selenaboranes are reported. Reactions of the monoanions of the syn- and anti-isomers of B18H22 with powdered selenium in THF variously give new macropolyhedral selenaboranes: 19-vertex [SeB18H19]- anion 1, 19-vertex [SeB18H21]- anion 2, 20-vertex [Se2B18H19]- anion 3, and 19-vertex [Se2B17H18]- anion 4. Single-cluster [hypho-Se2B6H9]- anion 5 and neutral arachno-Se2B7H9 6 also result. All of the macropolyhedrals 1, 2, 3, and 4 are characterized by NMR spectroscopy and mass spectrometry, and by single-crystal X-ray diffraction analyses. Anions 1 and 2 each consist of an 11-vertex subcluster joined by a common two-boron edge to a 10-vertex subcluster. Anion 3 consists of an 11-vertex subcluster joined by a common boron atom and an interboron link to an arachno-type 10-vertex subcluster. Unusually, anion 3 incorporates a hexagonal pyramidal intracluster structural motif in its 11-vertex subcluster. Anion 4 entails two arachno-type 10-vertex subclusters joined by a common boron atom, and with an additional intercluster boron-boron link. NMR data for syn-B18H22 and its mono- and dianions 7 and 8 and single-crystal X-ray diffraction results for these anions and also the monoanion 9 of anti-B18H22 are also reported. The oxaborane [µ-(8,9)-O-syn-B18H20]2- dianion 10 was serendipitously formed during the work and also characterized by a single-crystal X-ray diffraction study. Experimental NMR and structural findings are supported by DFT calculations throughout.

Ligand Lability Driven by Metal-to-Borane Pseudorotation: A Mechanism for Ligand Exchange.

The discovery of systems that interact with small molecules plays a vital facilitating role in the development of devices that show sensitivity to their surroundings and an ability to quickly relay chemical and physical information. Herein, we report on the reaction of [NiCl2(dppe)] with decaborane that produces in usable yield a new 11-vertex nickelaborane, [7,7-(dppe)-nido-7-NiB10H12] (1), which shows interesting reactivity and functionality toward carbon monoxide and ethylisonitrile. This contribution describes the synthesis and full structural characterization of 1 and its small-molecule EtNC and CO adducts, 2 and 3, and delineates the dynamic molecular behavior of all of these species in solution. This information sets a foundation from which more advanced work on this and related metallaborane systems can be conceived and provides a more general reference to how NMR spectroscopy, combined with DFT calculations, can be used to analyze the precise locomotion of labile ligands around a metal center held within a borane cluster.

A Reversible NO-Triggered Multiple Metallaborane Cluster Fusion by Ligand Expulsion/Addition from (PMe2Ph)4Pt2B10H10 to Afford (PMe2Ph)8Pt8B40H40 and (PMe2Ph)5Pt4B20H20.

The dimetallic boron hydride cluster, (PMe2Ph)4Pt2B10H10 (1-Pt2), is known to reversibly sequester small molecules (e.g., O2, CO, and SO2) across its Pt-Pt cluster vector. Here, we report the very different effect of the addition of nitric oxide (NO) to solutions of (1-Pt2) that prompts the elimination of some of its phosphine ligands and the autofusion of the resultant {(PMe2Ph)xPt2B10H10} units to afford the metallaborane conglomerates (PMe2Ph)8Pt8B40H40 (2-Pt8, 38%) and (PMe2Ph)5Pt4B20H20 (3-Pt4, 34%). Single-crystal X-ray studies of these multicluster assemblies reveal the links between the clusters to be a combination of both Pt-Pt bonds and Pt-µH-B 2-electron, 3-center bonds in (2-Pt8) and Pt-µH-B 2-electron, 3-center bonds in (3-Pt4). For compound (2-Pt8), the cluster assemblage can be effectively reversed by the addition of ethyl isonitrile (EtNC) to afford (EtNC)3(PMe2Ph)2Pt2B10H10 4 in quantitative yield. The compounds were characterized by mass spectrometry, multielement NMR spectroscopy, and single-crystal X-ray diffraction studies.

Swollen Polyhedral Volume of the anti-B18H22 Cluster via Extensive Methylation: anti-B18H8Cl2Me12.

Methylation of anti-B18H22 (1) affords the first example of alkyl substitution of terminal hydrogen atoms on the fluorescent octadecaborane-22 molecule to give highly methylated 2,2'-Cl2-1,1',3,3',4,4',7,7',8,8',10,10'-Me12-anti-B18H8 (2). This extensive chemical substitution leads to a swelling in the polyhedral volume of the 18-vertex boron atomic skeleton of the molecule and an enhancement of the absorption and solubility characteristics of this highly fluorescent molecule. We propose this "swollen polyhedral volume" to be the result of a marked increase in the relative positivity of the "cluster-only total charge" of the boron atomic skeleton caused by the combined electron-withdrawing capacity of the 12 methyl groups. Enhancement in the absorption and solubility properties may be crucial in the design of new borane-based laser materials.

A Series of Ultra-Efficient Blue Borane Fluorophores.

We present the first examples of alkylated derivatives of the macropolyhedral boron hydride, anti-B18H22, which is the gain medium in the first borane laser. This new series of ten highly stable and colorless organic-inorganic hybrid clusters are capable of the conversion of UVA irradiation to blue light with fluorescence quantum yields of unity. This study gives a comprehensive description of their synthesis, isolation, and structural characterization together with a delineation of their photophysical properties using a combined theoretical and experimental approach. Treatment of anti-B18H22 1 with RI (where R = Me or Et) in the presence of AlCl3 gives a series of alkylated derivatives, Rx-anti-B18H22-x (where x = 2 to 6), compounds 2-6, in which the 18-vertex octadecaborane cluster architectures are preserved and yet undergo a linear "polyhedral swelling", depending on the number of cluster alkyl substituents. The use of dichloromethane solvent in the synthetic procedure leads to dichlorination of the borane cluster and increased alkylation to give Me11-anti-B18H9Cl2 11, Me12-anti-B18H8Cl2 12, and Me13-anti-B18H7Cl2 13. All new alkyl derivatives are highly stable, extremely efficient (ΦF = 0.76-1.0) blue fluorophores (λems = 423-427 nm) and are soluble in a wide range of organic solvents and also a polystyrene matrix. The Et4-anti-B18H18 derivative 4b crystallizes from pentane solution in two phases with consequent multiabsorption and multiemission photophysical properties. An ultrafast transient UV-vis absorption spectroscopic study of compounds 4a and 4b reveals that an efficient excited-state absorption at the emission wavelength inhibits the laser performance of these otherwise remarkable luminescent molecules. All these new compounds add to the growing portfolio of octadecaborane-based luminescent species, and in an effort to broaden the perspective on their highly emissive photophysical properties, we highlight emerging patterns that successive substitutions have on the molecular size of the 18-vertex borane cluster structure and the distribution of the electron density within.

Macropolyhedral Nickelaboranes from the Metal-Assisted Fusion of KB9H14.

The reaction of K[arachno-B9H14] with [NiCl2(dppe)] produces four new 19-vertex macropolyhedral metallaboranes that result from borane cluster fusion: [9'-(dppe)-9'-Ni-anti-B18H20] (1) and isomeric [11'-(dppe)-11'-Ni-syn-B18H20] (2), together with the chlorine-substituted derivative of 1, [5'-Cl-9'-(dppe)-9'-Ni-anti-B18H19] (3), and the 18-vertex cluster compound [7'-(dppe)-7'-anti-NiB17H21] (4). Two closo 10-vertex single-cluster species, [1-(dppe)-1-closo-NiB9H7Cl2] (5) and [1-(dppe)-1-closo-NiB9H7Cl(OH)] (6), were also isolated from the reaction. The production of the metalated syn-octadecaborane isomer 2 from the fusion of two arachno-nonaborate clusters is the first such case to be observed; in all other reported cases fusion has resulted in products with the anti-octadecaboranyl bis-nido configuration.

Effect of Iodination on the Photophysics of the Laser Borane anti-B18H22: Generation of Efficient Photosensitizers of Oxygen.

Treatment of the laser borane anti-B18H22 (compound 1) with iodine in ethanol gives the monoiodinated derivative 7-I-anti-B18H21 (compound 2) in 67% yield, or, by reaction with iodine or ICl in the presence of AlCl3 in dichloromethane, the diiodinated derivative 4,4'-I2-anti-B18H20 (compound 3) in 85% yield. On excitation with 360 nm light, both compounds 2 and 3 give strong green phosphorescent emissions (λmax = 525 nm, ΦL = 0.41 and λmax = 545 nm, ΦL = 0.71 respectively) that are quenched by dioxygen to produce O2(1Δg) singlet oxygen with quantum yields of ΦΔ = 0.52 and 0.36 respectively. Similarly strong emissions can be stimulated via the nonlinear process of two-photon absorption when exciting with 720 or 800 nm light. The high quantum yields of singlet-oxygen production, coupled with the option of two-photon excitation, make compounds 2 and 3 promising O2(1Δg) photosensitizers. The molecular structures of compounds 2 and 3 were determined by single-crystal X-ray crystallographic studies as well as multinuclear NMR spectroscopy and mass spectrometry. Time-resolved UV-vis spectroscopy was used to delineate their photophysical properties, and the electronic-structure properties of the emitting species were determined by means of multiconfigurational quantum-chemistry computations.

A theoretical analysis of the structure and properties of B26H30 isomers. Consequences to the laser and semiconductor doping capabilities of large borane clusters.

Decaborane(14), nido-B10H14, is the major commercially available molecular building block in boron cluster chemistry. The condensation of two such {nido-B10} blocks gives the known isomers of B18H22- a molecule used in the fabrication of p-type semiconductors and capable of blue laser emission. Here, we computationally determine the structures and thermodynamic stabilities of 20 possible B26H30 regioisomers constructed from the fusion of three {nido-B10} blocks with the three subclusters conjoined by two-boron atom shared edges. In addition, density functional theory, time-dependent (TD)-DFT and multiconfigurational CASPT2 methods have been used to model and investigate the physical and photophysical properties of the three most stable of these isomers. Our findings predict these isomers to be potentially useful materials for the semiconductor industry, as high boron-content doping agents, and in the fabrication of new optical materials.

Phosphinic Acid Based Linkers: Building Blocks in Metal-Organic Framework Chemistry.

Metal-organic frameworks (MOFs) are a chemically and topologically diverse family of materials composed of inorganic nodes and organic linkers bound together by coordination bonds. Presented here are two significant innovations in this field. The first is the use of a new coordination group, phenylene-1,4-bis(methylphosphinic acid) (PBPA), a phosphinic acid analogue of the commonly used terephtalic acid. Use of this new linker group leads to the formation of a hydrothermally stable and permanently porous MOF structure. The second innovation is the application of electron-diffraction tomography, coupled with dynamic refinement of the EDT data, to the elucidation of the structure of the new material, including the localization of hydrogen atoms.

The synthesis and structural characterization of polycyclic derivatives of cobalt bis(dicarbollide)(1(-)).

The cobalt bis(dicarbollide) anion [(1,2-C2B9H11)2-3,3'-Co](-) (1(-)) is an increasingly important building block for the design of new biologically active compounds. Here we report the reactions of lithiated 1(-) with N-(ω-bromoalkyl)phthalimides Br-(CH2)n-N(CO)2NC6H4 (where n = 1 to 3) that give a number of new compounds substituted at dicarbollide carbon atom positions. For n = 2 and 3, substitution of the cobalt bis(dicarbollide) anion is accompanied by cyclocondensation of the organic moieties to give polycyclic ring structures attached to the cage. Predominant products correspond to oxazolo[2,3-a]isoindol-5(9bH)-1,2,3-dihydro-9b-yl)-(1-cobalt(III) bis(1,2-dicarbollide)(1(-)) (2(-)) and 1-(2H-[1,3]-oxazino[2,3-a]isoindol-6(10bH)-1,3,4-dihydro-10b-yl)-(1-cobalt(III) bis(1,2-dicarbollide)(1(-)) (4(-)) ions with isoindolone functions containing either five- or six-membered lateral oxazine rings. Additionally, products (tetrahydro-2-benzo[4,5]furan-1(3H)-1-[3,3]-yl-)-1,1'-µ-cobalt(III) bis(1,2-dicarbollide)(1(-)) (3(-)) and (2-(azetidin-yl-carbonyl)benzoyl-)-1-cobalt(III) bis(1,2-dicarbollide)(1(-)) (5(-)) were isolated, which display unusual cyclic structures featuring a bicyclic benzofuranone ring attached in a bridging manner by a quarternary carbon to two skeletal carbon atoms and a ketobenzoic acid amide substituent with a side azetidine ring. However, in the case of n = 1, only the anticipated methylene amine derivative [(1-NH2CH2-1,2-C2B9H11)(1',2'-C2B9H11)2-3,3'-Co](-) (6(-)) was isolated in low yield after cleavage of the phthalimide intermediate species. The molecular structures of all isolated cyclic products 2(-) to 5(-) were confirmed by single-crystal X-ray diffraction studies, and the structure of cobalt bis(dicarbollide)-1-CH2NH2 6(-) was delineated using density functional theory applied at BP86/AE1 level in combination with NMR spectroscopy. Thus, the synthetic method described herein presents a facile route to new cobalt bis(dicarbollide) derivatives substituted by polycyclic structural motifs with potential biological activity.

Tuning the photophysical properties of anti-B18H22: efficient intersystem crossing between excited singlet and triplet states in new 4,4'-(HS)2-anti-B18H20.

The tuning of the photophysical properties of the highly fluorescent boron hydride cluster anti-B18H22 (1), by straightforward chemical substitution to produce 4,4'-(HS)2-anti-B18H20 (2), facilitates intersystem crossing from excited singlet states to a triplet manifold. This subsequently enhances O2((1)Δg) singlet oxygen production from a quantum yield of ΦΔ âˆ¼ 0.008 in 1 to 0.59 in 2. This paper describes the synthesis and full structural characterization of the new compound 4,4'-(HS)2-anti-B18H20 (2) and uses UV-vis spectroscopy coupled with density functional theory (DFT) and ab initio computational studies to delineate and explain its photophysical properties.

"Activated Borane": A Porous Borane Cluster Polymer as an Efficient Lewis Acid-Based Catalyst.

Borane cluster-based porous covalent networks, named activated borane (ActB), were prepared by cothermolysis of decaborane(14) (nido-B10H14) and selected hydrocarbons (toluene, ActB-Tol; cyclohexane, ActB-cyHx; and n-hexane, ActB-nHx) under anaerobic conditions. These amorphous solid powders exhibit different textural and Lewis acid (LA) properties that vary depending on the nature of the constituent organic linker. For ActB-Tol, its LA strength even approaches that of the commonly used molecular LA, B(C6F5)3. Most notably, ActBs can act as heterogeneous LA catalysts in hydrosilylation/deoxygenation reactions with various carbonyl substrates as well as in the gas-phase dehydration of ethanol. These studies reveal the potential of ActBs in catalytic applications, showing (a) the possibility for tuning catalytic reaction outcomes (selectivity) in hydrosilylation/deoxygenation reactions by changing the material's composition and (b) the very high activity toward ethanol dehydration that exceeds the commonly used γ-Al2O3 by achieving a stable conversion of ∼93% with a selectivity for ethylene production of ∼78% during a 17 h continuous period on stream at 240 °C.

Distinct photophysics of the isomers of B18H22 explained.

The photophysics of the two isomers of octadecaborane(22), anti- and syn-B(18)H(22), have been studied by UV-vis spectroscopic techniques and theoretical computational methods. In air-saturated hexane, anti-B(18)H(22) shows fluorescence with a high quantum yield, Φ(F) = 0.97, and singlet oxygen O(2)((1)Δ(g)) production (Φ(Δ) ∼ 0.008). Conversely, isomer syn-B(18)H(22) shows no measurable fluorescence, instead displaying much faster, picosecond nonradiative decay of excited singlet states. Computed potential energy hypersurfaces (PEHs) for both isomers rationalize these data, pointing to a deep S(1) minimum for anti-B(18)H(22) and a conical intersection (CI) between its S(0) and S(1) states that lies 0.51 eV higher in energy. Such an energy barrier to nonradiative relaxation is not present in the PEH of syn-B(18)H(22), and the system therefore has sufficient initial energy on excitation to reach the (S(0)/S(1)) CI and to then decay to the ground state without fluorescence. The computational analysis of the geometries at stationary points along the PEH of both isomers shows that the determining factor for the dissimilar photophysics of anti- and syn-B(18)H(22) may be due to the significant differences in the geometrical rearrangements at their respective conical intersections. Thus, the syn isomer shows one very large, B-B elongation of 1.2 Å from 1.8 Å in the ground state to 3.0 Å at the CI, whereas the anti isomer shows smaller elongations (below 1 Å) in several B-B connectivities at its (S(0)/S(1))(CI). The absorbed energy in S(1) for the anti-B(18)H(22) is therefore redistributed vibrationally into several regions of the molecule rather than almost completely into a single vibrational mode as in the case for the syn isomer. The consequent prolonged S(1) lifetime for the anti isomer allows for relaxation via fluorescence.

Decaborane thiols as building blocks for self-assembled monolayers on metal surfaces.

Three nido-decaborane thiol cluster compounds, [1-(HS)-nido-B(10)H(13)] 1, [2-(HS)-nido-B(10)H(13)] 2, and [1,2-(HS)(2)-nido-B(10)H(12)] 3 have been characterized using NMR spectroscopy, single-crystal X-ray diffraction analysis, and quantum-chemical calculations. In the solid state, 1, 2, and 3 feature weak intermolecular hydrogen bonding between the sulfur atom and the relatively positive bridging hydrogen atoms on the open face of an adjacent cluster. Density functional theory (DFT) calculations show that the value of the interaction energy is approximately proportional to the number of hydrogen atoms involved in the interaction and that these values are consistent with a related bridging-hydrogen atom interaction calculated for a B(18)H(22)·C(6)H(6) solvate. Self-assembled monolayers (SAMs) of 1, 2, and 3 on gold and silver surfaces have been prepared and characterized using X-ray photoelectron spectroscopy. The variations in the measured sulfur binding energies, as thiolates on the surface, correlate with the (CC2) calculated atomic charge for the relevant boron vertices and for the associated sulfur substituents for the parent B(10)H(13)(SH) compounds. The calculated charges also correlate with the measured and DFT-calculated thiol (1)H chemical shifts. Wetting-angle measurements indicate that the hydrophilic open face of the cluster is directed upward from the substrate surface, allowing the bridging hydrogen atoms to exhibit a similar reactivity to that of the bulk compound. Thus, [PtMe(2)(PMe(2)Ph)(2)] reacts with the exposed and acidic B-H-B bridging hydrogen atoms of a SAM of 1 on a gold substrate, affording the addition of the metal moiety to the cluster. The XPS-derived stoichiometry is very similar to that for a SAM produced directly from the adsorption of [1-(HS)-7,7-(PMe(2)Ph)(2)-nido-7-PtB(10)H(11)] 4. The use of reactive boron hydride SAMs as templates on which further chemistry may be carried out is unprecedented, and the principle may be extended to other binary boron hydride clusters.

Reversible capture of small molecules on bimetallaborane clusters: synthesis, structural characterization, and photophysical aspects.

Metallaborane compounds containing two adjacent metal atoms, [(PMe(2)Ph)(4)MM'B(10)H(10)] (where MM' = Pt(2), 1; PtPd, 7; Pd(2), 8), have been synthesized, and their propensity to sequester O(2), CO, and SO(2) and to then release them under pulsed and continuous irradiation are described. Only [(PMe(2)Ph)(4)Pt(2)B(10)H(10)], 1, undergoes reversible binding of O(2) to form [(PMe(2)Ph)(4)(O(2))Pt(2)B(10)H(10)] 3, but solutions of 1, 7, and 8 all quantitatively take up CO across their metal-metal vectors to form [(PMe(2)Ph)(4)(CO)Pt(2)B(10)H(10)] 4, [(PMe(2)Ph)(4)(CO)PtPdB(10)H(10)] 10, and [(PMe(2)Ph)(4)(CO)Pd(2)B(10)H(10)] 11, respectively. Crystallographically determined interatomic M-M distances and infrared CO stretching frequencies show that the CO molecule is bound progressively more weakly in the sequence {PtPt} > {PtPd} > {PdPd}. Similarly, SO(2) forms [(PMe(2)Ph)(4)(SO(2))Pt(2)B(10)H(10)] 5, [(PMe(2)Ph)(4)(SO(2))PtPdB(10)H(10)] 12, and [(PMe(2)Ph)(4)(SO(2))Pd(2)B(10)H(10)] 13 with progressively weaker binding of the SO(2) molecule. The uptake and release of gas molecules are accompanied by changes in their absorption spectra. Nanosecond transient absorption spectroscopy clearly shows that the O(2) and CO molecules are liberated from the bimetallic binding site with high quantum yields of about 0.6. For 3, in addition to dioxygen release in the triplet ground state, singlet oxygen O(2)((1)Δ(g)) was also detected with a quantum yield <0.01. In most cases, the release and rebinding of the gas molecules can be cycled with little photodegradation of the compounds. Femtosecond transient absorption spectroscopy further reveals that the photorelease of the O(2) and CO molecules, from 3 and 4 respectively, is an ultrafast process taking place on a time scale of tens of picoseconds. For SO(2), the release is even faster (<1 ps), but only in the case of mixed metal PtPd adducts, most probably because of the metal-metal bonding asymmetry in the mixed metal clusters; for the corresponding symmetric Pt(2) and Pd(2) adducts, 5 and 13, the release of SO(2) is significantly slower (>1 ns). All these compounds may have potential to serve as light-triggered local and instantaneous sources of the studied gases.