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The ground- and excited-state structures were fully optimized for a series of neutral binuclear Au(I) thiolates, [Au[sub 2](dpm)(SCH[sub 2]S)] (1) (dpm=bis(diphosphino)methane), trans-[Au[sub 2](PH[sub 2]CH[sub 2]S)[sub 2]] (2), and trans-[Au[sub 2](SHCH[sub 2]S)[sub 2]] (3), by using the MP2 and CIS methods, respectively. The calculated Au[sup I]–Au[sup I] distances of about 3.0 Å in the ground state of the complexes are indicative of aurophilic attraction between the two Au(I) atoms, while in their excited states the separations are greatly shortened (about 2.7–2.9 Å). The promotion of Au d electron or S p electron into the bonding s[sub σ] and/or p[sub σ] lowest unoccupied molecular orbital of Au[sup I]–Au[sup I] results in such reinforcement of aurophilicity in the excited state. In the CIS calculations of the three Au(I) thiolates, we obtained the lowest-energy phosphorescent emission in the solid state for each of the complexes. The 462 nm emission of 1 was assigned as Au→S charge transfer (MLCT) transition. But for 3, the charge transfer localized on the Au centers, [sup 3]A[sub u](s[sub σ])→[sup 1]A[sub u](d[sub σ[sup *]]) (metal-centered charge transfer, MCCT), plays a main role in the 413 nm emission. Both the MCCT and MLCT transitions are important in the 323 nm emission of 2. The results indicated that Au[sup I]–Au[sup I] aurophilicity clearly influences luminescent properties of these complexes. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Binuclear uranyl (VI) and (V) complexes of a Pacman-like polypyrrolic macrocycle (H4L) were investigated using relativistic density functional theory. The reactivity of the bis-uranyl(Vl) complex (UO2)2(L) (2a) was explored computationally. Although 2a has not been obtained expeitmentally, its structural analogue [(UO2)(OH)K(THF)2(H2LMe)] has been synthesized recently. The high reactive activity of 2a originates from its unique butterfly like cation-cation structure, containing an active O center with easily broken U-O bonding and having unsaturated coordination sites of uranium(VI) along the equatorial plane. The present study indicates that 2a can react with water (Path 3) and hydronium (Path 4), which lead to the formation of a series of complexes with a triangle-like O=U=O=U=O skeleton. Path 3 results in an unusual complex containing a combined cis-uranyl/trans-uranyl cation-cation structure, (cis-UO2)(trans-UO2)(H2O)(L) (4b), where the oxo atom of the trans uranyl coordinates the uranium center of the cis-uranyl and the water bonds to the uranium of trans-uranyl in the equatorial plane. After a process of hydrogen transfer with an extremely low energy baffler (<1.5 kcal/mol), 4b is converted into a slightly more stable isomer (U2O3)(OH)2(L) (4a), where two hydroxyl groups link to two uranium atoms, respectively. In conjunction with previous studies, the free energies of reactions of 2a induced by isomerization (Path 1), proton (Path 2), water (Path 3), and hydrorrium (Path 4) were calculated in the gas phase and aqueous solution. Solvation stabilizes the free energy of the formation reactions of the neutral complexes but destabilizes that of the charged complexes. In these reactions, three pairs of isomers were obtained for binudear uranium(Vl) complexes, but only the most stable in each pair exists for the binuclear uranium(V) analogues. [ABSTRACT FROM AUTHOR]

To understand their photocatalytic activity and application in luminescent materials, a series of gold and rhodium phosphine complexes (mononuclear [Au[supI](PH[sub3])[sub2]][sup+] (1) and [Rh[supI](CNH)[sub2](PH[sub3])[sub2]][sup+] (2); homobinuclear [Au[supI][sub2](PH[sub2]CH[sub2]PH[sub2])[sub2]][sup2+] (6), and [Au[supII]Rh[supII](CNH)[sub2](PH[sub2]NHPH[sub2])[sub2]][sup2+] (7); and oxidized derivatives [A[supII]Rh[supII](CNH)[sub2](PH[sub2]CH[sub2]PH[sub2])[sub2]][sup4+] (8), [Au[supII]Rh[supII](CNH)[sub2](PH[sub2]NHPH[sub2])[sub2]Cl[sub3]][sup+] (9), and [Au[supII]Rh[supII](CNH)[sub2](PH[sub2]NHPH[sub2])[sub2]][sup4+] (10)) were investigated using ab initio methods and density functional theory. With the use of the MP2 method, the M-M' distances in 3-7 were estimated to be in the range of 2.76-3.02 Å, implying the existence of weak metal-metal interaction. This is further evident in the stretching frequencies and bond orders of M-M'. The two-electron oxidation from 5-7 to their respective partners 8-10 was shown to mainly occur in the gold-rhodium centers. Experimental absorption spectra were well reproduced by our time-dependent density functional theory calculations. The metal-metal interaction results in a large shift of d[subz[sup2]] → p[subz] transition absorptions in binuclear complexes relative to mononuclear analogues and concomitantly produces a low-lying excited state that is responsible for increasing visible-light photocatalytic activities. Upon excitation, the metal-centered transition and the metal-to-metal charge transfer strengthen the metal-metal interaction in triplet excited states for 3-6, while the promotion of electrons into the σ*(d[subz[sup2]]) orbital weakens the interaction in 9. [ABSTRACT FROM AUTHOR]

A comprehensive calculations were carried out to get a deep insight into the ground- and excited-state electronic structures and the spectroscopic properties for a series of [Pt(4-X–trpy)C≡CC6H4R]+ complexes (trpy = 2,2′,6′,2″-terpyridine; X = H, R = NO2 (1), Cl (2), C6H5 (3) and CH3 (4); R = Cl, X =CH3 (5) and C6H5 (6)). MP2 (second-order Møller–Plesset perturbation) and CIS (single-excitation configuration interaction) methods were employed to optimize the structures of 1–6 in the ground and excited states, respectively. The investigation showed that substituted phenylacetylide and trpy ligands only give rise to a small variation in geometrical structures but lead to a sizable difference in the electronic structures for 1–6 in the ground and excited states. The introduction of electron-rich groups into the phenylacetylide and/or terpyridyl ligands produces two different low-lying absorptions for 1 and 2–6, i.e., Pt(5d) → π∗(trpy) metal-to-ligand charge transfer (MLCT) mixed with π →π∗≡(CCPh) intraligand charge transfer (ILCT) for 1 and Pt(5d)/π(C≡CPh) → π∗(trpy) charge transfer (MLCT and LLCT) for 2–6. Remarkable electronic resonance on the whole Pt–CCPh–NO2 moiety for 1 may be responsible for the difference. Solvatochromism calculation revealed that only LLCT/MLCT transitions showed the solvent dependence, consistent with the experimental observations. [Copyright &y& Elsevier]

The binuclear gold phosphorus ylide complexes [Au I2(CH 2PH 2CH 2) 2] ( 1), [Au II2X 2(CH 2PH 2CH 2) 2] (X = Cl ( 2a), Br ( 2b), I ( 2c)), [Au III2X 4(CH 2PH 2CH 2) 2] (X = Cl ( 3a), Br ( 3b)), and [Au IAu IIIX 2(CH 2PH 2CH 2) 2] (X = Cl ( 4a), Br ( 4b)) were explored using density functional theory and ab initio methods. The use of methods, basis sets, and substituent effects confirmed our calculations. The analyses on their electronic structures reveal that two- and four-electron oxidation from 1to 2− 4mainly occurs at the gold centers, resulting in their different coordination geometry features and metal−metal interactions as well as spectroscopic properties. Bond-order and frequency calculations provided the evidence for the weak Au−Au bonding interaction in 1, 3, and 4and an approximate Au−Au single bond in 2. Unrestricted MP2 calculations showed that the triplet excited-state structures of 1, 2a, and 3aare minimum points on the potential energy surface. Upon excitation, the Au−Au distances of 1and 3ashorten while that of 2aincreases. This is closely correlated with the promotion of electrons into the bonding or antibonding orbitals of the gold centers. [ABSTRACT FROM AUTHOR]

The structures of trans-M2(CN)4(PH2CH2PH2)2(M Pt (1), Pd (2), and Ni (3)), trans-Pt2X4(PH2CH2PH2)2(X Cl (4) and Br (5)), and trans-M(CN)2(PH3)2(M Pt (6), Pd (7), and Ni (8)) in the ground state were optimized using the MP2 method. Frequency calculations reveal that the weak metal−metal interaction is essentially attractive for 1, 2, 4, and 5but not for 3. The TD-DFT calculations associated with the polarized continuum model (PCM) were performed to predict absorption spectra in CH2Cl2solution. Experimental spectra are well reproduced by our results. With respect to analogous mononuclear d8complexes (6−8), a large red shift of the absorption wavelength was calculated for the binuclear d8complexes (1−3). Relative to 1with unsaturated CN-donors, introduction of saturated halogen donors into 4and 5changes their electronic structures, especially the HOMO and LUMO. The TD-DFT and subsequent unrestricted MP2 calculations predict that 1produces the lowest-energy d → p emission while 2−5favor the d → d emissions, agreeing with experimental observations. [ABSTRACT FROM AUTHOR]

The structures of [Pt2(pop)4]4-, [Pt2(pcp)4]4-, and related species [Pt2(pop)4X2]4- and [Pt2(pop)4]2- in the ground states (pop = P2O5H22-, pcp = P2O4CH42- and X = I, Br, and Cl) were optimized using the second-order Møller-Plesset perturbation (MP2) method. It is shown that the Pt-Pt distances decrease in going from [Pt2(pop)4]4- to [Pt2(pop)4X2]4- to [Pt2(pop)4]2-. This is supported by the analyses of their electronic structures. The calculated aqueous absorption spectra at the time-dependent density functional theory (TD-DFT) level agree with experimental observations. The unrestricted MP2 method was employed to optimize the structures of (Pt2(pop)4]4- and [Pt2(pcp)4]4 in the lowest-energy triplet excited states. The Pt-Pt contraction trend is well reproduced in these calculations. For [Pt2(pop)4]4-, the Pt-Pt distance decreases from 2.905 Å in the ground state to 2.747 Å in the excited state, which is comparable to experimental values of 2.91-2.92 Å and 2.64-2.71 Å, respectively. On the basis of the excited-state structures of such complexes, TD-DFT predicts the solution emissions at 480 and 496 nm, which is closer to the experimental values of 512 and 510 nm emissions, respectively. [ABSTRACT FROM AUTHOR]

Based on their MP2 optimized structures in the ground states, we obtained solution absorption spectra for trans-[PtII(C≡CR)2(PH3)2] (R = H (1) and Ph (2)) and trans-[PtII(C≡CH)2(PH2CH2PH2)]2 (3) under the time-dependent density functional theory calculations. These absorptions agree with experimental observations. The unrestricted MP2 optimization performed for 3 in the lowest-energy triplet excited state shows that upon excitation the PtPt distance shortens about 0.347 Å with respect to the 3.188 Å one in the ground state. The UMP2 calculations estimated that its 3[σ*(dz2)σ(pz)] excited state produces the 531 nm emission, corresponding to the 580 nm one of trans-[PtII(C≡CPh)2(PPh2CH2PPh2)]2 in the solid state at 298 K. [Copyright &y& Elsevier]

Electronic structures and spectroscopic properties of the binuclear head-to-tail [Au2(PH2CH2SH)2]2+ (1) complex were investigated by ab initio calculations. The solvent effect of the complex in the acetonitrile solution was taken into account by the weakly solvated [Au2(PH2CH2SH)2]2+ (2) moiety in the calculations. The ground-state geometries of 1 and 2 were fully optimized by the MP2 method, while their excited-state structures were optimized by the CIS method. Aurophilic attraction apparently exists between the two Au(I) atoms in the ground state and is strongly enhanced in the excited state. A high-energy phosphorescent emission was calculated at 337 nm for 1 in the absence of the interactions with solvent molecules and/or counteranion in solid state; however the lowestenergy emission of 2 was obtained at 614 nm with the nature of ³Au(sσ → ¹Ag(dσ*) (metal-centered, MC) transition. The coordination of acetonitrile to the gold atom in solution results in a dramatic red shift of emission wavelength. The investigations on the head-to-tail [Au2,(PH2CH2SCH3)2]2+ (5) and [Au2(PH2CH2SCH3)2]2+·(MeCN)2 (6) moieties indicate that the CH3 substituent on the S atom causes blue shifts of emission wavelength for 5 and 6 with respect to 1 and 2. By comparison between Au(I) thioether 1 and head-to-tail Au(I) thiolate [Au2(PH2CH2CH2S)2] (7), it is concluded that the S→Au dative bonding results in evidently different transition characteristics from the S-Au covalent bonding in the Au(I) thioether/thiolate complexes. [ABSTRACT FROM AUTHOR]

Actinyl and actinyl-transition metal complexation by a polypyrrolic macrocycle with anthracenyl linkers between the N4-donor compartments was evaluated using relativistic density functional theory which predicts that a highly unusual cofacial bis-actinyl structure complex is stable. [ABSTRACT FROM AUTHOR]

Electronic structures and spectroscopic properties of a series of nitrido-osmium (VI) complex ions with acetylide ligands, [OsN(C=CR)4]- (R==H, (1), CH3 (2), and Ph (3)) were investigated theoretically. The structures of the complexes were fully optimized at the B3LYP and CIS level for the ground states and excited states, respectively. The calculated bond lengths of Os=N (1.639 Å in 1, 1.642 Å in 2, and 1.643 Å in 3) and Os–C (2.040 Å in 1, 2.043 Å in 2, and 2.042 Å in 3) in ground state agree well with the experimental results. The bond length of Os=N bond is lengthened by ca. 0.13 Å in the A 3B2 excited state compared to the 1A1 ground state, which is consistent with the lower vibration frequency of ν(Os–N) (∼780 cm-1) in the excited state than that (∼1175 cm-1) in the ground state. Among the calculated dipole-allowed absorptions at λ>250 nm, the intense absorption at 261 nm for 1, 266 nm for 2, and 300 nm for 3 were attributed to the 1[π(C=C)]→1[π*(N=Os)+π*(C=C)], 1[π(C=C)]→1[π*(N=Os)+π*(C=C)], and 1[π(C=CPh)]→1[π*(N=Os)+π*(C=CPh)], respectively. The lowest energy absorption at λmax=393 nm for 1, 400 nm for 2, and 400 nm for 3 were assigned as 1[dxy(Os)+π(C=C)]→1[π*(N=Os)+π*(C=C)], 1[dxy(Os)+π(C=C)]→1[π*(N=Os)+π*(C=C)], and 1[dxy(Os)+π(C=CPh)]→1[π*(N=Os)+π*(C=CPh)], respectively. The calculated phosphorescence emission at λmax=581 nm for 1, 588 nm for 2, and 609 nm for 3 were originated from 3[(π*(N=Os)+π*(C=C))1(dxy(Os)+π(C=C))1], 3[(π*(N=Os)+π*(C=C))1(dxy(Os)+π(C=C))1], and 3[(π*(N=Os)+π*(C=CPh))1(dxy(Os)+π(C=CPh))1] excited state, respectively. [ABSTRACT FROM AUTHOR]

Dimeric complexes (RuIIPz)2 have been investigated using density functional theory (DFT), where Pz is a porphyrazine ligand that features a 16-atom, 18-π-electron cyclic polyene aromatic skeleton. Structural optimizations in various configurations and spin states indicate that (RuPz)2 favours a Pz-Pz staggered conformer over an eclipsed one; the paramagnetic triplet state with the staggered configuration is found as the global ground state. This agrees with experimental magnetic results of (RuOEPor)2 (OEPor=octaethylporphyrin) and (RuPc)2 (Pc=phthalocyanine). The Ru-Ru bond length was optimized to be 2.38Å, close to the experimental bond length of 2.40-2.41Å. The Ru2 doubly bonded nature has been evidenced by the Ru-Ru stretching vibrational frequency of 202cm-1, bond energy of 30.7 kcal mol-1, and electronic arrangement of σ²π4(nonbonding-δ)4(π*)². Further confirmation was obtained from high-level wave function theory calculations (complete active space self-consistent field and n-electron valence state second-order perturbation theory). Associated with the solvation of the explicit pyridine accounting for the first coordination sphere and the implicit continuum model for the long-range interaction, the electronic spectra of tetrapyrrolic ruthenium complex were calculated at the time-dependent DFT level. [ABSTRACT FROM AUTHOR]

On the basis of relativistic density functional theory calculations, homo- and heterovalent binuclear uranium complexes of a polypyrrolic macrocycle in a U-O-U bridging fashion have been investigated. These complexes show a variety of oxidation states for uranium ranging from III to VI, which have been confirmed by the calculated electron-spin density on each metal center. An equatorially 5-fold uranyl coordination mode is suitable for hexavalent uranium complexes, while silylation of the uranyl oxo is favored by pentavalent uranium. Uranyl oxo ligands are not required anymore for the coordination environment of tetra- and trivalent uranium because of their replacement by strong donors such as tetrahydrofuran and iodine. Optimization of binuclear UVI-UIII complexes with various coordinating modes of UIII, donor numbers, and donor types reveals that 0.5-1.0 electron has been transferred from UIII to UVI. Consequently, UV-UIV complexes are more favorable. Electronic structures and formation reactions of several representative uranium complexes were calculated. For example, a 5f-based s(U-U) bonding orbital is found in the diuranium(IV) complex, rationalizing the fact that it shows the shortest U-U distance (3.82 Å) among the studied binuclear complexes. [ABSTRACT FROM AUTHOR]

Two new uranyl arsonates, Zn(UO2)(PhAsO3)2LH2O [L = 1,10-phenanthroline (1) and 2,2'-bipyridine (2)], have been synthesized by hydrothermal reactions of phenylarsonic acid, L, and ZnUO2(OAc)4·7H2O. Single-crystal X-ray analyses demonstrate that these two compounds are isostructural and exhibit one-dimensional chains in which UVI and ZnII cations are direcdy connected by the yl oxygen atoms and additionally bridged by arsonate groups. Both compounds represent the first examples of uranyl arsonates with heterometallic cation-cation interactions. [ABSTRACT FROM AUTHOR]

Well-crystallized and hexagonal wurtzite ZnO was synthesized with nanocellulose using a facile hydrothermal method. Many highly active (001) facets were retained in the obtained ZnO nanocrystals, presumably due to interaction between the polar facet of ZnO and the nanocellulose. Given its effective surface area, the synthesized ZnO exhibited good photocatalytic activity of degrading methylene blue. Its degradation efficiency reached 94.4% within 30 min (UV irradiation power of 6 W), which was 34% higher than that of Degussa TiO2 P25. The ZnO photocatalyst also exhibited excellent reusability, confirmed by no obvious abatement after its being re-used for 8 cycles. These ZnO nanomaterials were synthesized using renewable nanocellulose derived from cotton. This environmentally friendly and cost-effective approach is anticipated to be applied in the future synthesis of small-sized ZnO photocatalysts. [ABSTRACT FROM AUTHOR]

Hydrothermal reactions of uranyl acetate and a series of transition metal acetates with a carboxyphosphinate and auxiliary N-donor ligands gave rise to the formation of eight heterometallic uranyl-organic assemblies, namely, Co(im)2(UO2)3(L)4 (1), Zn(bpi)(UO2)(L)2 (2), Cd(dib)(UO2)(L)2 (3), M(dib)(UO2)2(L)3 (M = Cd (4), Mn (5)), and [M(dib)2(H2O)2][(UO2)3(L)4]·nH2O (M = Co (6, n = 2), Ni (7, n = 2), Cu (8, n = 0)) [H2L = (2-carboxyethyl)(phenyl)phosphinic acid (CPP), im = imidazole, bpi =1-(biphenyl-4-yl)-1H-imidazole, dib =1,4-di(1H-imidazol-1-yl)benzene]. Single-crystal X-ray diffraction (XRD) analysis of 1 reveals a layered structure of UO6, UO7, and CoO4N2 units that are linked by the carboxyphosphinate ligands. Imidazole molecules modify the layer by coordinating to Co centers. Similarly, 2 is a mixed zinc-uranyl carboxyphosphinate with different topological two-dimensional structure and the decorated moiety is a bpi coligand. When in the presence of bridging dib coligands, the mixed cadmium-uranyl carboxyphosphinate sheets of 3 are pillared by dib forming a framework structure. The isostructures of 4 and 5 are also pillared frameworks constructed by a mixed heterometallic uranyl phosphinate layered subnet that is different from that of 3. The structures of 6-8 are isotype and very special in that they consist of distinct [M(dib)2(H2O)2]n2n+ cationic and [(UO2)3(L)4]n2n- anionic subnets. Such two sheets are packed alternatively and interact via hydrogen bond forming three-dimensional supramolecular structures. [ABSTRACT FROM AUTHOR]

A Schiff-base polypyrrolic ligand(H4L) can accommodatetwo U3+ions and form a Pacman-like complex [U2(L)]2+according to relativistic density functional theory.Sixteen species, featuring four structural models in four electronicstates, are energetically stable. Ligand flexibility, lack of axialrestriction, and suitable U–N interactions allow the two U3+ions to stretch freely over a wide range, in contrast toU2@Cn(n=60, 74, 80) studied previously. Diverse U3+–U3+interactions are found. The quintet state of the Out–Inmodel, which is calculated to be the global ground state both includingand excluding the spin–orbit coupling energy, likely showsa weak single U2bond. In both verticaland tiltIn–In species, a triple bond isfound. It is composed of two two-electron–two-center bondsand two one-electron–two-center bonds; moreover, the tiltconformer is almost isoenergetic with Out–In.The Out–Out species shows no U···U bonding.Comparison with explicitly THF-solvated diuranium complexes is alsoaddressed. [ABSTRACT FROM AUTHOR]

A family of di-, tri-, and tetranuclear copper(I) complexes supported by length-controlled silaamidinate ligands have been synthesized to show short CuI-CuI distances (2.43-2.62 Å) and feature a linear or bent metal-metal arrangement, which is elucidated by a relativistic density functional theory calculation. [ABSTRACT FROM AUTHOR]

A series of uranyl--organic coordination polymers have been hydrothermally synthesized by using a variety of carboxylic ligands, 3,3'-((2-((3-carboxyphenoxy)methyl)-2-methylpropane-1,3-diyl)bis(oxy))dibenzoic acid (H3L¹), 4,4'-(3-(4-carboxyphenethyl)-3-hydroxypentane-l,5-diyl)-dibenzoic acid (H3L²), chelidamic acid (H2L³), and benzoic acid (HL4) in the presence of N-bearing coligands, including 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), l-([l,l'-biphenyl]-4-yl)-lH-imidazole (bpi), and l,4-di(LH-imidazol-l-yl)benzene (dib). Compounds (U02)(HL¹) (l) and Zn(H20)3(U02)2(0)(0H)(L²)-H20 (2) are constructed by semirigid ligands. The former is a one-dimensional ribbon-like structure with UO7 pentagonal bipyramids as the building unit, while the latter adopts a tetramer of U07 pentagonal bipyramids to build a layered structure. Mononuclear U07 pentagonal bipyramids are connected by L³ groups to generate a two-dimensional arrangement of UO2(L³)(H2dib)0S (3), in which the protonated dib molecules provide space filling and form π--π interactions with the layers. Compounds U02(L³)(phen) (4), U02(L³)2(Hbpi)2 (5), and U02(L4)2(bipy) (6) are molecular complexes, in which 4 and 6 are neutral, and 5 comprises protonated bpi as the counterion. The uranyl center in compound 4 is chelated by one phen and one L³ group to form a UO5N2 pentagonal bipyramid, while in compound 5, two L³ groups are coordinated to an uranyl center, producing a UO8 polyhedron. Compound 6 consists of a U06N2 polyhedron of uranyl unit coordinated by one bipy and two benzoate groups. Compounds Zn(phen)3[(U02)(C204)(L4)]2 (7) and Zn(bpi)2(U02)(0)-(C204)os(L4) H20 (8) feature one-dimensional structures. In 7, U07 pentagonal bipyramids are alternatively connected by oxalate groups to form the chain, in which unidentate benzoate groups are coordinated to the uranium atoms. Zn(phen)3 cations fill the void space of the chains to compensate the negative charge. Differendy, the chain of 8 can be seen as the heterometallic tetramer of U07 and Zn02N2 polyhedra connected by oxalate groups, and then bpi and benzoate groups are coordinated to the chain. All of the compounds have been characterized by IR and photoluminescent spectroscopy, and compounds 2, 3, 5, 6, and 8 exhibit characteristic emissions of uranyl cations. [ABSTRACT FROM AUTHOR]

To advance the understanding of the chemical behavior of actinides, a series of trans-bis(imido) uranium(VI) complexes, U(NR)2(THF)2(cis-I2) (2R; R = H, Me, 'Bu, Cy, and Ph), U(NR)2(THF)3(trans-I2) (3R; R = H, Me, 'Bu, Cy, and Ph) and U(N'Bu)2(THF)3(cis-I2) (3'Bu'), were investigated using relativistic density functional theory. The axial Uâ•N bonds in these complexes have partial triple bonding character. The calculated bond lengths, bond orders, and stretching vibrational frequencies reveal that the Uâ•N bonds of the bis-imido complexes can be tuned by the variation of their axial substituents. This has been evidenced by the analysis of electronic structures. 2H, for instance, was calculated to show iodine-based high-lying occupied orbitals and U(f)-type low-lying unoccupied orbitals. Its Uâ•N bonding orbitals, formed by U(f) and N(p), occur in a region of the relatively low energy. Upon varying the axial substituent from H to 'Bu and Ph, the Uâ•N bonding orbitals of 2'Bu and 2Ph are greatly destabilized. We further compared the Uâ•E (E = N and O) bonds of 2H with 3H and their uranyl analogues, to address effects of the equatorial tetrahydrofuran (THF) ligand and the E group. It is found that the Uâ•N bonds are slightly weaker than the Uâ•O bonds of their uranyl analogues. This is in line with the finding that cis-UNR2 isomers, although energetically unfavorable, are more accessible than cis-UO2 would be. It is also evident that 2H and 3H display lower Uâ•(NH) stretching vibrations at 740 cm-1 than the Uâ•O at 820 cm-1 of uranyl complexes. With the inclusion of both solvation and spin-orbit coupling, the free energies of the formation reactions of the bis-imido uranium complexes were calculated. The formation of the experimentally synthesized 3Me, 3Ph, and 2'Bu are found to be thermodynamically favorable. Finally, the absorption bands previously obtained from experimental studies were well reproduced by time-dependent density functional theory calculations. [ABSTRACT FROM AUTHOR]

A family of uranium diphosphonates have been hydrothermally synthesized through the reaction of ethylenediphosphonic acid (EDP, H4L) and uranyl nitrate/zinc uranyl acetate in the presence of organic templates, such as tetraethyl ammonium (NEt4+), 4,4'-bipyridine (bipy), and 1,10-phenanthroline (phen). The U022+ in U02(H20)(H2L)- (EDP-U1) is equatorially five-coordinated by four phosphonate groups and one aqua ligand, forming a pentagonal bipyramid. Each EDP ligand is doubly protonated and chelates three U022+, resulting in a layered structure. Compounds (NEt4)2(UO2)3(HL)2(H2L)-4H20 (EDP-U2) and (H2bipy)U02L (EDP-U3) have the same layered structure in which NEt4+ and protonated bipy fill in the uranyl--phosphonate interlayers, respectively, and play a role to balance the negative charges. Different from that in EDP-U1, the U022+ exists in the form of a U06 tetragonal bipyramid and is surrounded by four different EDP ligands in EDP-U2 and EDP-U3. (Hphen)2(U02)2(H2L)3 (EDP-U4) features a three-dimensional framework structure with large elliptical channels along the c axis (1.3 X 1.1 nm²). Monoprotonated phen molecules fill in these channels and hold together through strong π···π interactions. All of the four compounds have been characterized by IR and photoluminescent spectroscopy. Their characteristic emissions have been attributed as transition properties of uranyl cations. The ion-exchange study indicates that [Co(en)3]3+ could partially replace the protonated phen molecules. [ABSTRACT FROM AUTHOR]

Six uranyl phosphonates and sulfonates have been hydrothermally synthesized, namely, (H2tib)-[(UO2)3(PO3C6H5)4]⋅2H2O (UPhP-1), Zn(pi)2(UO2)(PO3C6H5)2 (UPhP-2), Zn(dib)(UO2)(PO3C6H5)2⋅2H2O (UPhP-3), (HTEA)[(UO2)(5-SP)] (USP-1), (Hdib)2[(UO2)2(OH)(0)(5-SP)] (USP-2), and Zn-(phen)3(UO2)2(3-SP)2 (USP-3) (tib = 1,3,5-tri(1H-imidazol-1-yl)benzene, pi = 1-phenyl-1H-imidazole, dib = 1,4-di(1H-imidazol-1-yl)benzene, TEA = triethylamine, phen - 1,10-phenanthroline, 5-SP = 5-sulfoisophthalic acid, and 3-SP = 3-sulfoisophthalic acid). UPhP-1 has been determined to be a layered structure constructed by UO7 pentagonal bipyramids, UO6 octahedra, and phenylphosphonates. Protonated tib plays a role in balancing the negative charge and holding its structure together. UPhP-2 is made up of UO6 octahedra, ZnO2N2 tetrahedra and PO3C tetrahedra in phenylphosphonates, forming a ID assembly, which is stabilized by chelate phen ligand. Further connection of such chainlike structure via dib yields a 2D layered architecture of UPhP-3. Although sulfonate group possesses similar tetrahedral structure as the phosphonate group, a unidentated coordination mode is only found in this work. UO7 pentagonal bipyramids are linked by 5-SP to form the layered assembly of USP-1. USP-2 also consists of the same sulfonate ligand, but features tetranulear uranyl clusters. Similarly, protonated TEA and dib molecules enable stabilization of their structures, respectively. Formed by dinuclear uranyl cluster and 3SP ligand, USP-3 appears as a 1D arrangement, in which Zn(phen)3 acts as the counterion to compensate the negative charge. All of these compounds have been characterized by IR and photoluminescent spectroscopy. Their characteristic emissions have been attributed as transition properties of uranyl cations. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a family of new inorganic--organic hybrid uranyl diphosphonates based on 1-hydroxyethylidenediphosphonic acid (H4L) linker by using hydrothermal method. These compounds, (Hbpi)[(UO2)(H2O)(HL)]-H2O(UP- 1), represents ID structure, (Hbpi)[(UO2)(H2O)(HL)] (UP-2), (H2dib)0.5[(UO2)- (H2O)(HL)] (UP-3), and [(UO2)(H2O)(H2L)-2H2O (UP-4) feature 2D architectures, (H2bipy){[(UO2)(H2O)]2[(UO2)(H2O)2](L)2}-2H2O (UP-5), and (H3O)2{[(UO2 ) - (H2O)]3(L)2}-2H20 (UP-6) adopt 3D networks (bpi: l-(biphenyl-4-yI)-lH-imidazole, dib: l,4~di(lH-imidazol-I-yl)ben2ene, bipy: 2,2'-bipyridine). Among them, UP-1, UP-2, UP-3, and UP-4 possess the same structural building unit but with different structures. UP-5 and UP-6 feature the same UO2/L ratio of 3:2 but a different structural building unit. Photoluminescence studies reveal that UP-5 displays characteristic emissions of uranyl cations. Ion-exchange experiments demonstrate that the H3O+ in UP-6 can be easily and selectively exchanged by monovalent cations including Na+, K+, Cs+, and Ag+ cations, whereas the framework retains identical as confirmed by single-crystal X-ray diffractions. [ABSTRACT FROM AUTHOR]

Iridium(III) complexes with N-heterocyclic (NHC) ligands including fac-Ir(pmb)3 (1), mer-Ir(pmb)3 (2), (pmb)2Ir(acac) (3), mer-Ir(pypi)3 (4), and fac-Ir(pypi)3 (5) [pmb = 1-phenyl-3H-benzimidazolin-2-ylidene, acac = acetoylacetonate, pypi = 1-phenyl-5H-benzimidazolin-2-ylidene; fac = facial, mer = meridional] were investigated theoretically. The geometry structures of 1–5 in the ground and excited state were optimized with restricted and unrestricted DFT (density functional theory) methods, respectively (LANL2DZ for Ir atom and 6-31G for other atoms). The HOMOs (highest occupied molecular orbitals) of 1–3 are composed of d(Ir) and π(phenyl), while those of 4 and 5 are contributed by d(Ir) and π(carbene). The LUMOs (lowest unoccupied molecular orbitals) of 1, 2, 4, and 5 are localized on carbene, but that of 3 is localized on acac. The calculated lowest-lying absorptions with TD-DFT method based on Perdew-Burke-Erzenrhof (PBE) functional of 1 (310 nm), 2 (332 nm), and 3 (347 nm) have MLcarbeneCT/ILphenyl→carbeneCT (MLCT = metal-to-ligand charge transfer; ILCT = intraligand charge transfer) transition characters, whereas those of 4 (385 nm) and 5 (389 nm) are assigned to MLcarbeneCT/ILcarbene→carbeneCT transitions. The phosphorescences calculated by TD-DFT method with PBE0 functional of 1 (386 nm) and 2 (388 nm) originate from 3MLcarbeneCT/3ILphenyl→carbeneCT excited states, but those of 4 (575 nm) and 5 (578 nm) come from 3MLcarbeneCT/3ILcarbene→carbeneCT excited states. The calculated results showed that the carbene and phenyl groups act as two independent chromophores in transition processes. Compared with 1 and 2, the absorptions of 4 and 5 are red-shifted by increasing the effective π-conjugation groups near the Ccarbene atom. We predicated that (pmb)2Ir(acac) is nonemissive, because the LUMO of 3 is contributed by the nonemissive acac ligand. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [ABSTRACT FROM AUTHOR]

The ground and the excited state geometries, electronic structures, absorption and emission spectra as well as the substituent effects of a series of osmium (II) diimine complexes Os(N^N)(C≡N)2(PH3)2 [N^N = 2,2′−bipyridine (bpy) 1; 4,4-di-tert-butyl-2,2′-bipyridine (dbubpy) 2; 4,4-di-methoxy-2,2′-bipyridine (dmobpy) 3; 4,4-di-chloro-2,2′-bipyridine (dcbpy) 4] were investigated by DFT and ab initio methods. At the TD-DFT and PCM level, the lowest-lying absorptions of 1−4 at 483, 467, 463, and 522 nm are dominantly assigned to a {[dxy(Os)] → [π*(N^N)]} transition with MLCT character. The calculated phosphorescence of 1−4 at 635, 605, 598, and 683 nm can be described as originating from 3{[dxy(Os)] [π*(N^N)]} excited state. The spectra are blue-shifted by adding electron-donating substituents of t−butyl and —OCH3 on the N^N ligands, but red-shifted by adding electron-withdrawing group —Cl. [Copyright &y& Elsevier]

Electronic structures, absorptions and emissions of a series of (ppy)2Ir(acac) derivatives (ppy = 2- phenylpyridine; acac = acetoylacetonate) with fluoro substituent on ppy ligands were investigated theoretically. The ground and excited states geometries were fully optimized at B3LYP/LANL2DZ and CIS/LANL2DZ level, respectively. The HOMO is composed of d(Ir) and π(C∧N), while the LUMO is localized on C∧N ligand. The absorptions and emissions in CH2Cl2 media were calculated under the TD–DFT level with PCM model. The lowest-lying absorption of these complexes is dominantly attributed to metal-to-ligand and intraligand charge transfer (MLCT/ILCT) transitions and the emission of them originates from 3MLCT/3ILCT excited states. The absorption and emission of these complexes are blue-shifted by increasing the number of fluoro on phenyl, but the spectra are red-shifted by adding fluoro on pyridyl. While a single fluoro of different substituted site on phenyl results in different extent blue-shift to the spectra. [ABSTRACT FROM AUTHOR]

The geometries, electronic structures, and spectroscopic properties of Ir(ppy) 2(N^N) +( 1) (N^N = 2-phenyl-1 H-imidazo[4,5- f][1,10]phenanthroline, ppy = 2-phenylpyridine), Ir(ppy) 2(N^N) +·F −( 2), Ir(ppy) 2(N^N) +·CF 3COOH ( 3/ 3a), and Ir(ppy) 2(N^N) +·CH 3COO −( 4) were investigated theoretically. The ground and the excited state geometries of 1− 4were optimized at the B3LYP/LANL2DZ and UB3LYP/LANL2DZ levels, respectively. The optimized geometries agree well with the corresponding experimental results. The HOMOs of 1− 4and 3aare composed of π(ppy) and d(Ir), and the LUMOs of 1, 2, 3a, and 4are contributed by π*(N^N), whereas the LUMO of 3is composed of π*(N^N) and π*(CF 3COOH). Under the time-dependent density functional theory level with polarized continuum model model, the absorption and phosphorescence in CH 2Cl 2media were calculated on the basis of the optimized ground and excited state geometries, respectively. The lowest-lying absorptions of 1(412 nm) and 3/ 3a(409/419 nm) have MLCT/LLCT transition characters, and those of 2(448 nm) and 4(427 nm) are contributed by ILCT character. The calculated lowest-energy triplet excited states responsible for phosphorescence of 1(519 nm) and 3/ 3a(661/702 nm) have mixing 3MLCT/ 3LLCT/ 3ILCT characters, but those of 2and 4only have 3ILCT but without 3MLCT character, which is the reason for the no-emissive character of 2and 4. Moreover, the phosphorescence character of 3is hardly changed by different addition sites of CF 3COOH group ( 3a). The calculated results also showed that complex 1is more suitable for an F −sensor than for CF 3COOH and CH 3COO −sensors. [ABSTRACT FROM AUTHOR]

A series of ruthenium(ll) complexes, [Ru(tcterpy)(NCS)3]4 (OH), [Ru(Htcterpy)(NCS)3]3 (1H), [Ru(H2tcterpy)(NCS)3]2 (2H), and [Ru(H3tcterpy)(NCS)3] (3H) (tcterpy = 4,4',4"-tricarboxy-2,2':6',2"-terpyridine), are investigated theoretically to explore their electronic structures and spectroscopic properties. The geometry structures of the complexes in the ground and excited states are optimized by the density functional theory and single-excitation configuration interaction methods, respectively. The absorption and emission spectra of the complexes in gas phase and solutions (ethanol and water) are predicted at the TDDFT(B3LYP) level. The calculations indicate that the protonation effect slightly affects the geometry structures of the complexes in the ground and excited states but leads to significant change in the electronic structures. In cases of both absorptions and emissions, the energy levels of HOMOs and LUMOs for OH-3H decrease dramatically as a result of the introduction of the COOH groups. The protonation much stabilizes the unoccupied orbitals with respect to the occupied orbitals. Thus, both the absórptions and emissions are red-shifted from OH to 3H. The phosphorescence of OH-3H are attributed to tcterpyridine -~ d(Ru)/ NCS (3MLCT/3LLCT) transitions. The solvent media can influence the molecular orbital distribution of the complexes; as a consequence, the spectra calculated in the presence of the solvent are in good agreement with the experimental results. The MLCT/LLCT absorptions of OH in ethanol and water are red-shifted relative to that in the gas phase. However, the MLCT/LLCT absorptions of the protonated complexes (1H-3H) are blue-shifted in ethanol and water with respect to the gas phase. Similarly, the solvent effect causes a blue-shift of the phosphorescent emission for OH-3H. [ABSTRACT FROM AUTHOR]

A series of trans-(FcC2n)RU2(Y-DMBA)4(C2mFc) with n, m = 1 and 2 and Y-DMBA as N,N'-dimethylbenzamidinate or N,N'-dimethyl-(3-methoxy)benzamidinate have been synthesized and characterized. The intramolecular Fc…Fc distances, established through single-crystal X-ray diffraction studies, range from 11.6 to 16.6 A. Results from both voltammetric and spectroelectrochemical studies indicate that the (-C2n)Ru2(Y-DMBA)4(C2m-) fragments are among the most efficient mediators of intramolecular hole transfer. Density-functional calculations offer both the insight on the ground-state electronic properties and unambiguous assignment for the observed electronic absorptions. [ABSTRACT FROM AUTHOR]