A diamine-bis(phenolate) chromium(III) complex, {CrCl[O(2)NN'](BuBu)}(2) catalyzes the copolymerization of cyclohexene oxide with carbon dioxide. The synthesis of this metal complex is straightforward, and it can be obtained in high yields. This catalyst incorporates a tripodal amine-bis(phenolate) ligand, which differs from the salen or salan ligands typically used with Cr and Co complexes that have been employed as catalysts for the synthesis of such polycarbonates. The catalyst reported herein yields low molecular weight polymers with narrow polydispersities. Structural and spectroscopic details of this complex along with its copolymerization activity for cyclohexene oxide and carbon dioxide are presented.

We report here an enhancement in photovoltage for dye-sensitized solar cells (DSSCs) where halogen-bonding interactions exist between a nucleophilic electrolyte species (I(-)) and a photo-oxidized dye immobilized on a TiO2 surface. The triarylamine-based dyes under investigation showed larger rate constants for dye regeneration (kreg) by the nucleophilic electrolyte species when heavier halogen substituents were positioned on the dye. The open-circuit voltages (VOC) tracked these kreg values. This analysis of a homologous series of dyes that differ only in the identity of two halogen substituents provides compelling evidence that the DSSC photovoltage is sensitive to kreg. This study also provides the first direct evidence that halogen-bonding interactions between the dye and the electrolyte can bolster DSSC performance.

A homologous series of donor-π-acceptor dyes was synthesized, differing only in the identity of the halogen substituents about the triphenylamine (TPA; donor) portion of each molecule. Each Dye-X (X=F, Cl, Br, and I) was immobilized on a TiO2 surface to investigate how the halogen substituents affect the reaction between the light-induced charge-separated state, TiO2 (e(-) )/Dye-X(+) , with iodide in solution. Transient absorption spectroscopy showed progressively faster reactivity towards nucleophilic iodide with more polarizable halogen substituents: Dye-F < Dye-Cl < Dye-Br < Dye-I. Given that all other structural and electronic properties for the series are held at parity, with the exception of an increasingly larger electropositive σ-hole on the heavier halogens, the differences in dye regeneration kinetics for Dye-Cl, Dye-Br, and Dye-I are ascribed to the extent of halogen bonding with the nucleophilic solution species.

A diamine-bis(phenolate) chromium(III) complex, {CrCl[O2NN'](BuBu)}2 catalyzes the copolymerization of propylene oxide with carbon dioxide. The synthesis of this metal complex is straightforward and it can be obtained in high yields. This catalyst incorporates a tripodal amine-bis(phenolate) ligand, which differs from the salen or salan ligands typically used with Cr and Co complexes that have been employed as catalysts for the synthesis of such polycarbonates. The catalyst reported herein yields low molecular weight polymers with narrow polydispersities when the reaction is performed at room temperature. Performing the reaction at elevated temperatures causes the selective synthesis of propylene carbonate. The copolymerization activity for propylene oxide and carbon dioxide, as well as the coupling of carbon dioxide and styrene oxide to give styrene carbonate are presented.

Two lithium amine-bis(phenolate) and four chromium(III) amine-bis(phenolate) complexes have been prepared. The diprotonated tripodal tetradentate ligand precursors 2-tetrahydrofurfuryl-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol), H(2)[O(2)NO](BuMe); 2-tetrahydrofurfuryl-N,N-bis(2-methylene-4,6-tert-butylphenol), H(2)[O(2)NO](BuBu); 2-pyridylamino-N,N-bis(2-methylene-4,6-methylphenol), H(2)[O(2)NN'](MeMe); and 2-pyridylamino-N,N-bis(2-methylene-4,6-tert-butylphenol), H(2)[O(2)NN'](BuBu); can be lithiated using n-butyllithium. Isolation of the Li(2)[O(2)NO](RR') compounds generates dimeric {Li(2)[O(2)NO](RR')}(2) (R = t-Bu, R' = Me in 1 and R = R' = t-Bu in 2) in the solid state as shown by single-crystal X-ray diffraction. The lithiated ligands were used to prepare a series of Cr(III) complexes. Monometallic complexes are obtained when prepared and purified under strictly anhydrous conditions, giving CrCl(THF)[O(2)NO](RR') (R = t-Bu, R' = Me in 3 and R = R' = t-Bu in 4). However, bimetallic Cr complexes are obtained upon recrystallization in air, where adventitious water reacts with the complex resulting in protonation of one of the phenolate groups of the ligand and generating hydroxide, which bridges two Cr(III) centres. Solid-state single-crystal X-ray diffraction studies of {CrCl[O(2)NN'](MeMe)}(mu-HO){CrCl[HO(2)NN'](MeMe)}, 5, and {CrCl[O(2)NN'](BuBu)}(mu-HO){CrCl[HO(2)NN'](BuBu)}, 6, were performed. The paramagnetic Cr(III) complexes were also characterized by UV-vis spectroscopy, mass spectrometry and magnetic measurements.

Lithium compounds of tetradentate amino-bis(phenolato)-tetrahydrofuranyl ligands, Li(2)[L1] (1) and Li(2)[L2] (2) (where [L1] = 2-tetrahydrofuranyl-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate), and [L2] = 2-tetrahydrofuranyl-N,N-bis(2-methylene-4,6-tert-butylphenolate)) were characterized by multinuclear solution NMR and solid-state (6)Li and (7)Li NMR spectroscopy. The proligands, n-propylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol), (H(2)[L3]) and benzylamino-N,N-bis(2-methylene-4,6-di-tert-amylphenol), H(2)[L4] were reacted with n-butyllithium in THF to give the related dilithium compounds Li(2)[L3] (4) and Li(2)[L4] (5), respectively. The pyridine adduct of 1, (py)(2)Li(2)[L1] (3) and complexes 4 and 5 have been structurally characterized by single-crystal X-ray diffraction and NMR spectroscopy. The reactivity of these complexes for the ring-opening polymerization of rac-lactide, as well as the influences of monomer concentration, monomer/Li molar ratio, polymerization temperature and time, were studied.

Eight new iron(III) amine-bis(phenolate) complexes are reported. The reaction of anhydrous FeX(3) salts (where X = Cl or Br) with the diprotonated tripodal tetradentate ligands 2-tetrahydrofurfurylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenol), H(2)L1, 2-tetrahydrofurfurylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol), H(2)L2, and 2-methoxyethylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenol), H(2)L3, 2-methoxyethylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol), H(2)L4 produces the trigonal bipyramidal iron(III) complexes, L1FeCl (1a), L1FeBr (1b), L2FeCl (2a), L2FeBr (2b), L3FeCl (3a), L3FeBr (3b), L4FeCl (4a), and L4FeBr (4b). All complexes have been characterized using electronic absorption spectroscopy, cyclic voltammetry and room temperature magnetic measurements. Variable temperature magnetic data were acquired for complexes 2b, 3a and 4b. Variable temperature Mössbauer spectra were obtained for 2b, 3a and 4b. Single crystal X-ray molecular structures have been determined for proligand H(2)L4 and complexes 1b, 2b, and 4b.

Ahomologous series of donor-p-acceptor dyes was synthesized,d iffering only in the identity of the halogen substituents about the triphenylamine (TPA; donor) portion of each molecule.E ach Dye-X (X = F, Cl, Br,a nd I) was immobilized on aT iO 2 surface to investigate how the halogen substituents affect the reaction between the light-induced charge-separated state,T iO 2 (e À )/Dye-X + ,w ith iodide in solution. Transient absorption spectroscopys howed progressively faster reactivity towards nucleophilic iodide with more polarizable halogen substituents: Dye-F < Dye-Cl < Dye-Br < Dye-I.Given that all other structural and electronic properties for the series are held at parity,w ith the exception of an increasingly larger electropositive s-hole on the heavier halogens,t he differences in dye regeneration kinetics for Dye-Cl, Dye-Br,a nd Dye-I are ascribed to the extent of halogen bonding with the nucleophilic solution species.A halogen bond is an attractive non-covalent interaction between ah alogen and an ucleophilic species.[1-6] Halogen bonding has been characterized in fluid solution and in solid state materials with applications in crystal engineering,anion sensing,s elf-assembly,b iotechnology,a nd catalysis. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Reported herein is kinetic evidence indicating that halogen bonding also occurs at the solid-liquid interface.T his finding was enabled by systematic characterization of ah omologous series of donor-p-acceptor dyes,v arying only in the identity of two halogen atoms,a tt itanium dioxide acetonitrile interfaces (Scheme 1). Light-induced interfacial electron transfer experiments revealed enhanced photoreactivity when larger,m ore polarizable halogens were employed. This result offers compelling evidence that halogen bonding assists the regeneration of the photo-oxidized dyes,w hich is supported by computational data. Theo bservation that halogen bonding can occur at solid-liquid interfaces and has ameasurable effect on charge-transfer behavior, suggests that it can be exploited in applications,i ncluding solar energy conversion schemes.