Nestlike Silver(I) Thiolate Clusters with Tunable Emission Color Templated by Heteroanions.

Four silver thiolate clusters, [H3 O][(Ag3 S3 )(BF4 )@Ag27 (tBuS)18 (hfac)6 H2 O]⋅H2 O (1; hfac = hexafluoroacetylacetone), [(Ag3 S3 )(CF3 CO2 )@Ag30 (tBuS)16 (CF3 CO2 )9 (CH3 CN)4 ]⋅CF3 CO2 ⋅4 CH3 CN (2), [(Ag3 S3 )(MoO4 )@Ag30 (tBuS)16 (CF3 CO2 )9 (CH3 CN)4 ]⋅2 CH3 CN (3), and [(Ag3 S3 )(CrO4 )@Ag30 (tBuS)16 (CF3 CO2 )9 (CH3 CN)4 ]⋅4 CH3 CN (4), were isolated. They have similar nestlike structures assembled by an [Ag3 S3 ]3- template together with one of the BF4 - , CF3 CO2 - , MoO4 2- , or CrO4 2- anions. Interestingly, the solid-state emissions of 2-4 are dependent on the templating anions and are tunable from green to orange and then to red by changing the template from CF3 CO2 - to MoO4 2- and to CrO4 2- , and this may be correlated to the charge transfer between these templates to metal atoms. This work helps to understand the templating role of heteroanions and the relationship between structure and properties.

Construction of Silver Clusters Capped by Zwitterionic Ethynide Ligands.

A zwitterionic ligand 3-(triethylammonio)propyne (TAP) has been employed to construct nine silver ethynide compounds for the first time. Single-crystal X-ray analyses reveal that compounds 1 and 2 are silver ethynide assemblies based on the Ag3 subunits and clusters 3-8 are small discrete clusters of Ag3, Ag6, Ag8, and Ag12, respectively, ligated by the bulky TAP ligand with different auxiliary ligands. In addition, upon acquiring the tripod-like tBuPO32-, a unprecedented 80 nuclei silver ethynide cluster was isolated and determined to be [(CF3CO2)5@Ag80(TAP)14(tBuPO3)16(CF3CO2)24]19+ by crystallography and thermogravimetric analysis. The C1 symmetry of Ag80 was deconstructed to be two [Ag40(TAP)7(tBuPO3)8(CF3CO2)12]12+ secondary building subunits arranged in a cross way, with five CF3CO2- trapped in the center. These results highlight that the elaborate selection of ethynide ligands is of great importance in the synthesis of novel silver ethynide clusters.

Hybrid Rare-Earth(III)/Bismuth(III) Clusters Assembled with Phosphonates.

tert-Butylphosphonic acid and rare-earth precursors are employed to construct four trinuclear rare-earth phosphonate clusters, RE3( tBuPO3)2(hfac)5(CH3OH)8]·2CH3OH (RE = Eu, Y, Pr, and Sm; hfac = hexafluoroacetylacetonate), which are composed of three RE3+ ions alternately bridged by two phosphonates. With the introduction of bismuth oxido diketonate, [Bi9O7(hfac)13], three different types of rare-earth/bismuth phosphonate clusters, Bi12RE2 (RE = Pr and Sm), Bi6Eu7, and Bi6Y9, are successfully obtained via variation of the reaction conditions, and they are the first reported examples of bismuth-oxo clusters encapsulated by cyclic rare-earth-oxo or rare-earth/bismuth-oxo phosphonate clusters, respectively. These clusters show obvious absorption in the UV region, and the Eu-containing clusters exhibit bright-red fluorescence.

High-Nuclearity Heterometallic tert-Butylethynide Clusters Assembled with tert-Butylphosphonate.

tert-Butylphosphonic acid and lanthanide precursors were employed to construct two high-nuclearity hybrid silver(I)-ytterbium(III) phosphonate clusters: compound 1 consists of a Ag16 ethynide cluster fused with a trinuclear hydroxoytterbium phosphonate cluster, whereas compound 2 is composed of two Ag16 ethynide clusters bridged by a hexanuclear oxo/hydroxoytterbium phosphonate cluster. Using transition-metal-substituted lacunary polyoxotungstates in place of the lanthanide reactant, new phosphonate-functionalized silver(I)-copper(II) ethynide clusters [Ag34 Cu6 (3) and Ag37 Cu6 (4)] and silver(I) ethynide clusters [Ag51 (5) and Ag72 (6)] were obtained. The structures of complexes 3-6 feature core-shell arrangements, in which silver(I)-copper(II) or silver(I) ethynide cluster shells stabilized by peripheral phosphonate ligands enclose different kinds of tungstate core templates.

Influence of Aggregation on the Structure and Fluorescent Properties of a Tetraphenylethylene Derivative: a Theoretical Study.

The case that aggregation has a large influence on the structure and fluorescent properties of 5-(4-(1,2,2-triphenylvinyl)phenyl)thiophene-2-carbaldehyde (P4 TA) is investigated in detail herein by employing quantum mechanics and molecular mechanics. Besides the isolated molecule, the aggregated molecule in water and in the crystalline state was studied by focusing on the comparison of photoelectronic properties, including the geometrical and electronic structures at ground and excited states, emission and internal conversation properties. For the aggregation state, the intermolecular interaction was used to explain the difference in structure, emission color and intensity of different polymorphs. The noticeable contribution from low-frequency region, corresponding to the four phenyl rings twisting vibration, to the Huang-Rhys factor and reorganization energy, as well as the possible potential energy surface crossing between S0 and S1 states for isolated molecules was considered as the reason of its aggregation-induced emission (AIE) performance. Importantly, the aggregation process in water simulated at the same time helps us to have a deeper understanding of the AIE behavior of P4 TA, which also provides another perspective to explore the AIE phenomenon in theory.

Structure-Directing Role of Phosphonate in the Synthesis of High-Nuclearity Silver(I) Sulfide-Ethynide-Thiolate Clusters.

Phosphonate ligands as structure-directing components have been employed to construct four new high-nuclearity silver(I) sulfide-ethynide-thiolate clusters, in which silver(I) aggregates tBuC≡C⊃Ag3, tBuC≡C⊃Ag4, and 2tBuC≡C⊃Ag7 are bridged by tBuS- ligands to engender respective silver(I) ethynide-thiolate clusters functioning as integral shell components, which are supported by phosphonate ligands. In each silver(I) sulfide-ethynide-thiolate cluster, a different encapsulated silver sulfide cluster serves as a core template.

High-Nuclearity Silver Thiolate Clusters Constructed with Phosphonates.

The n-butylphosphonate ligand has been employed to construct three new silver(I) thiolate compounds. Single-crystal X-ray analysis revealed that complexes 1 and 2 are Ag48 and Ag51 coordination chain polymers, while 3 contains a discrete Ag48 cluster, in which three different kinds of silver(I) thiolate cluster shells enclose three different phosphonate-functionalized silver(I) cluster cores, respectively. The structures of clusters in 1-3 feature three three-shell arrangements, S@Ag12 @(nBuPO3 )9 @Ag36 S23 , S@Ag11 @(nBuPO3 )7 (MoO4 )2 @Ag40 S27 and MoO4 @Ag12 @(nBuPO3 )8 S6 @Ag36 S24 , respectively.

Theoretical analysis of naproxen reaction with sulfate and hydroxyl radicals in the aqueous phase: Investigating reactive sites and reaction kinetics.

In this study, we have utilized theoretical calculations to predict the reaction active sites of naproxen when reacting with radicals and to further study the thermodynamics and kinetics of the reactions with ·OH and SO4-·. The evidence, derived from the average local ionization energy and electrostatic potential, points to the naphthalene ring as the preferred site of attack, especially for the C2, C6, C9, and C10 sites. The changes in Gibbs free energy and enthalpy of the reactions initiated by ·OH and SO4-· ranged between -19.6 kcal/mol - 26.3 kcal/mol and -22.3 kcal/mol -18.5 kcal/mol, respectively. More in-depth investigation revealed that RA2 pathway for ·OH exhibited the lowest free energy of activation, suggesting this reaction is more inclined to proceed. The second-order rate constant results indicate the ·OH attacking reaction is faster than reactions initiated by SO4·-, yet controlled by diffusion. The consistency between theoretical findings and experimental data underscores the validity of this computational method for our study.

Theoretical characterization and design of small molecule donor material containing naphthodithiophene central unit for efficient organic solar cells.

To seek for high-performance small molecule donor materials used in heterojunction solar cell, six acceptor-donor-acceptor small molecules based on naphtho[2,3-b:6,7-b']dithiophene (NDT) units with different acceptor units were designed and characterized using density functional theory and time-dependent density functional theory. Their geometries, electronic structures, photophysical, and charge transport properties have been scrutinized comparing with the reported donor material NDT(TDPP)2 (TDPP = thiophene-capped diketopyrrolopyrrole). The open circuit voltage (V(oc)), energetic driving force(ΔE(L-L)), and exciton binding energy (E(b)) were also provided to give an elementary understanding on their cell performance. The results reveal that the frontier molecular orbitals of 3-7 match well with the acceptor material PC61 BM, and compounds 3-5 were found to exhibit the comparable performances to 1 and show promising potential in organic solar cells. In particular, comparing with 1, system 7 with naphthobisthiadiazole acceptor unit displays broader absorption spectrum, higher V(oc), lower E(b), and similar carrier mobility. An in-depth insight into the nature of the involved excited states based on transition density matrix and charge density difference indicates that all S1 states are mainly intramolecular charge transfer states with the charge transfer from central NDT unit to bilateral acceptor units, and also imply that the exciton of 7 can be dissociated easily due to its large extent of the charge transfer. In a word, 7 maybe superior to 1 and may act as a promising donor candidate for organic solar cell.

An accurate and efficient method to predict the electronic excitation energies of BODIPY fluorescent dyes.

Recently, the extreme learning machine neural network (ELMNN) as a valid computing method has been proposed to predict the nonlinear optical property successfully (Wang et al., J. Comput. Chem. 2012, 33, 231). In this work, first, we follow this line of work to predict the electronic excitation energies using the ELMNN method. Significantly, the root mean square deviation of the predicted electronic excitation energies of 90 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives between the predicted and experimental values has been reduced to 0.13 eV. Second, four groups of molecule descriptors are considered when building the computing models. The results show that the quantum chemical descriptions have the closest intrinsic relation with the electronic excitation energy values. Finally, a user-friendly web server (EEEBPre: Prediction of electronic excitation energies for BODIPY dyes), which is freely accessible to public at the web site: http://202.198.129.218, has been built for prediction. This web server can return the predicted electronic excitation energy values of BODIPY dyes that are high consistent with the experimental values. We hope that this web server would be helpful to theoretical and experimental chemists in related research.

Solvatochromic behavior of chiral mesoporous metal-organic frameworks and their applications for sensing small molecules and separating cationic dyes.

Two anionic metal-organic frameworks (MOFs) with 1D mesoporous tubes (1) and chiral mesoporous cages (2) have been rationally constructed by means of a predesigned size-extended hexatopic ligand, namely, 5,5',5''-(1,3,5-triazine-2,4,6-triyl)tris- (azanediyl)triisophthalate (TATAT). Charge neutrality is achieved by protonated dimethylamine cations. Notably, the two MOFs can be used to separate large molecules based on ionic selectivity rather than the size-exclusion effect so far reported in the literature. Owing to the imino triazine backbone and carboxyl groups of the hexatopic ligand, which provide important host-guest interactions, rare solvatochromic phenomena of 1 and 2 are observed on incorporating acetone and ethanol guests. Furthermore, guest-dependent luminescence properties of compound 2 were investigated, and the results show that luminescence intensity is significantly enhanced in toluene and benzene, while quenching effects are observed in acetone and ethanol. Thus, compound 2 may be a potential material for luminescent probes.

Ag6 Cu8 (C=CAr)14 (DPPB)2 : A Rigid Ligand Co-Protected Bimetallic Silver(I)-Copper(I) Cluster with Room-Temperature Luminescence.

Metal clusters have become increasingly important in various applications, with ligands playing a crucial role in their construction. In this study, we synthesized a bimetallic cluster, Ag6 Cu8 (C=CAr)14 (DPPB)2 (Ag6 Cu8 ), using a rigid acetylene ligand, 3,5-bis(trifluoromethyl)phenylacetylide. Through single-crystal structure characterization, we discovered that the butterfly-shaped Ag2 Cu2 motifs were subject to distortion due to steric hindrance imposed by the rigid ligand. These motifs assembled together through shared vertices and edges. Mass spectrometry analysis revealed that the primary fragments detected during electrospray ionization (ESI) testing corresponded to the Ag2 Cu2 motifs. Furthermore, we conducted a comprehensive investigation of the cluster's solution properties employing 31 P NMR, UV-vis absorption, and photoluminescent measurements. In contrast to previously reported Ag/Cu bimetallic clusters protected by flexible ligands, Ag6 Cu8 protected by rigid ligands exhibited intriguing room temperature fluorescence properties alongside excellent thermal stability. DFT calculations on Ag6 Cu8 and Ag6 Cu8 with the rigid aromatic ring removed revealed that the presence of the rigid aromatic ring can lower the electronic energy levels of the cluster, and reduce the energy gap from 4.05 eV to 3.45 eV. Moreover, the rigid ligand further suppressed the non-radiative transition process, leading to room temperature fluorescence emission.

Theoretical insight into the origin of large stokes shift and photophysical properties of anilido-pyridine boron difluoride dyes.

The geometric and electronic structures and photophysical properties of anilido-pyridine boron difluoride dyes 1-4, a series of scarce 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives with large Stokes shift, are investigated by employing density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to shed light on the origin of their large Stokes shifts. To this end, a suitable functional is first determined based on functional tests and a recently proposed index-the charge-transfer distance. It is found that PBE0 provides satisfactory overall results. An in-depth insight into Huang-Rhys (HR) factors, Wiberg bond indices, and transition density matrices is provided to scrutinize the geometric distortions and the character of excited states pertaining to absorption and emission. The results show that the pronounced geometric distortion due to the rotation of unlocked phenyl groups and intramolecular charge transfer are responsible for the large Stokes shift of 1 and 2, while 3 shows a relatively blue-shifted emission wavelength due to its mild geometric distortion upon photoemission, although it has a comparable energy gap to 1. Finally, compound 4, which is designed to realize the rare red emission in BODIPY derivatives, shows desirable and expected properties, such as high Stokes shift (4847 cm(-1)), red emission at 660 nm, and reasonable fluorescence efficiency. These properties give it great potential as an ideal emitter in organic light-emitting diodes. The theoretical results could complement and assist in the development of BODIPY-based dyes with both large Stokes shift and high quantum efficiency.

A comparative study of [Ag11(iPrS)9(dppb)3]2+ and [Ag15S(sBuS)12(dppb)3]+: templating effect on structure and photoluminescence.

Atomically precise silver clusters with tunable photoluminescence (PL) properties have attracted extensive attention due to their great value for basic science and future applications. Here, we report that the addition of a sulfido template into a triangular thiolated silver cluster [Ag11(iPrS)9(dppb)3]·2CF3SO3·CH3OH (Ag11, dppb = 1,4-bis(diphenylphosphino)butane), which is emissive at 660 nm under ambient conditions, produced another silver cluster [S@Ag15(sBuS)12(dppb)3]·CF3SO3·H2O (Ag15) that displays 716 nm emission with a 56 nm redshift aided by the ligand sec-butyl mercaptan. The sulfido template, which affects the geometrical and electronic structures, results in a redshift of Ag11 room-temperature PL as a result of opening up the template-to-metal charge transfer (TMCT) and disturbing the electronic transition between the metal core and ligands at the periphery.

Controllable synthesis of porous tubular carbon by a Ag+-ligand-assisted Stöber-silica/carbon assembly process.

Herein, in this study, we utilized Ag+-ligand interactions for critically regulating the morphology of carbon by the Stöber-silica/carbon co-assembly method for the first time. Tetraethyl orthosilicate (TEOS) and resorcinol/formaldehyde (RF) assemble upon dictation by Ag+ and pyridyl-functionalized surfactants, producing porous carbon tubes (RF1) with a high surface area of 696 m2 g-1 and accessible mesopores ∼15 nm in size. Furthermore, when using tetrapropyl orthosilicate (TPOS) with a slower hydrolysis rate than that of TEOS, carbon tubes (RF2) with enhanced uniformity and a surface area as high as 2112 m2 g-1 are generated. Additionally, when using dopamine hydrochloride instead of RF as a carbon precursor, tubular polydopamine (TDA) with lengths of tens of microns is fabricated, which exhibits excellent catalytic activity toward oxygen reduction reactions in alkaline solutions due to its unique structural feature, a high surface area of 1350 m2 g-1, metallic silver remains of 8.3 wt%, and a rich nitrogen content of 3.6 wt%. This work sheds light on the engineering of a micellar soft template and synthesizing novel nanostructures by the extension of the Stöber method.

tert-Butyl thiol and pyridine ligand co-protected 50-nuclei clusters: the effect of pyridines on Ag-SR bonds.

Constructing silver(i)-thiolate clusters from simple building blocks usually involves elusive self-assembly processes and remains a long-standing challenge. In this work, we report 6 silver(i)-thiolate clusters protected by pyridines, namely, [Ag3(tBuS)2(Py)(NO3)]n (Py = pyridine) (1), [Ag10(tBuS)6(Py)6(CF3CO2)4]·3Py (2), [Ag12(iPrS)6(Py)8(NO3)6]·2H2O (3), Ag12(iPrS)6(Py)8(CF3CO2)6 (4), Ag12(iPrS)6(4-ap)6(NO3)6 (4-ap = 4-aminopyridine) (5), and [Ag50S13(tBuS)20(Py)12]·4BF4·4Py·4CH3OH·2H2O (6). Single-crystal X-ray crystallography analysis reveals that six clusters are constructed by four types of structural blocks, including the PyAg(tBuS)2 monomer, Py2Ag2(tBuS)2 dimer, Py3Ag3(tBuS)3 trimer and (4-ap)6Ag6(iPrS)6 hexamer. Notably, cluster 6 consists of a rhombic dodecahedron S@Ag14 kernel with 12 interstitial S2- atoms encapsulated by 8 µ4-tBuS- ligands, as well as six unique butterfly-like (Py)2Ag6(tBuS)2 staple motifs composed of a Py2Ag2(tBuS)2 dimer and four silver ions. Moreover, it is found that pyridine ligands have important influence on the construction of silver thiolate clusters and their Ag-SR bond lengths.

Density Functional Studies on Photophysical Properties of Boron-Pyridyl-Imino-Isoindoline Dyes: Effect of the Fusion.

In this work, to make out the aryl-fusion effect on the photophysical properties of boron-pyridyl-imino-isoindoline dyes, compounds 1-5 were theoretically studied through analyses of their geometric and electronic structures, optical properties, transport abilities, and radiative (k r) and non-radiative decay rate (k nr) constants. The highest occupied molecular orbitals of aryl-fused compounds 2-5 are higher owing to the extended conjugation. Interestingly, aryl fusion in pyridyl increases the lowest unoccupied molecular orbital (LUMO) level, while isoindoline decreases the LUMO level; thus, 4 and 5 with aryl fusion both in pyridyl and isoindoline exhibit a similar LUMO to 1. Compounds 4 and 5 show relatively low ionization potentials and high electron affinities, suggesting a better ability to inject holes and electrons. Importantly, the aryl fusion is conducive to the decrease of k IC. The designed compound 5 exhibits a red-shifted emission maximum, low λh, and low k IC, which endow it with great potential for applications in organic electronics. Our investigation provides an in-depth understanding of the aryl-fusion effect on boron-pyridyl-imino-isoindoline dyes at molecular levels and demonstrates that it is achievable.

A theoretical investigation on the thermally activated delayed fluorescence characteristics of the isomers of DTCBPy.

It has been reported that 3, 5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-phenyl)(pyridin-4-yl)meth (DTCBPy) is an efficient thermally activated delayed fluorescence (TADF) molecule. We designed a series of the isomeric molecules (2-5) of DTCBPy (1) by changing the position of nitrogen atom in the acceptor and the substituent position of donor units. The highest occupied molecular orbitals (HOMO) of 1-5 are all delocalized over the donor units, and the lowest unoccupied molecular orbitals (LUMO) are located on the acceptor unit. As expected from frontier molecular orbital analysis, the singlet-triplet energy splitting (ΔEST) values of 1-5 are in a small range from 0.087 to 0.147 eV, indicating the easy realization of reverse intersystem crossing from the lowest triplet to singlet excited states. However, the structural modification has a significant influence on the fluorescence radiative rate (kr), which varies from 3.49× 106 to 2.04 × 107 s-1 for 1-5. This work is expected to provide valuable information for synthesizing highly efficient TADF materials based on DTCBPy.

High-nuclearity silver ethynide clusters containing polynucleating oxygen donor ligands.

Polynucleating oxygen donor ligands as precursors have been employed to construct three high-nuclearity heterometallic ethynide clusters. Compound 2 consists of a Cl@Ag12 ethynide cluster capped by two trinuclear organooxotin phosphonate clusters [(nBuSn)3(µ3-O)(tBuPO3)3(OMe)(OH)2]2-. Compound 3 consists of a Ag8 ethynide cluster fused with a nonanuclear oxo-bismuth phosphonate cluster [Bi9O6(tBuPO3)9(tBuPO3H)]4-, while compound 4 is composed of two Cl@Ag15 ethynide clusters bridged by a hexanuclear oxo/hydroxo-bismuth phosphonate cluster [Bi6O4(OH)4(tBuPO3)6(hfac)2(CF3COO)2]10-.

Density functional studies on photophysical properties and chemical reactivities of the triarylboranes: effect of the constraint of planarity.

The geometric and electronic structures, absorption spectra, transporting properties, chemical reactivity indices and electrostatic potentials of the planar three-coordinate organoboron compounds 1-2 and twisted reference compound Mes(3)B, have been investigated by employing density functional theory (DFT) and conceptual DFT methods to shed light on the planarity effects on the photophysical properties and the chemical reactivity. The results show that the planar compounds 1-2 exhibit significantly lower HOMO level than Mes(3)B, owing to the stronger electronic induction effect of boron centers. This feature conspicuously induces a blue shifted absorption for 1, although 1 seemingly possesses more extended conjugation framework than Mes(3)B. Importantly, the reactivity strength of the boron atoms in 1-2 is much lower than that in Mes(3)B, despite the fact that the tri-coordinate boron centers of 1-2 are completely naked. The interesting and abnormal phenomenon is caused by the strong p-π electronic interactions, that is, the empty p-orbital of boron center is partly filled by π-electron of the neighbor carbon atoms in 1-2, which are confirmed by the analysis of Laplacian of the electron density and natural bond orbitals. Furthermore, the negative electrostatic potentials of the boron centers in 1-2 also interpret that they are not the most preferred sites for incoming nucleophiles. Moreover, it is also found that the planar compounds 1-2 can act as promising electron transporting materials since the internal reorganization energies for electron are really small.