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1.
Chem Commun (Camb) ; 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32666980

RESUMO

Two mixed-metal hydride clusters, corresponding to x = 3 and 4, were structurally characterized from a set of atomically precise heptanuclear clusters, CuxAg7-x(H){S2P(OiPr)2}6 (x = 1-6). An interstitial hydride lying at the center of a tricapped tetrahedral cage was located and refined anisotropically by using X-ray data, and its presence acertained by multinuclear NMR spectroscopy and DFT calculations.

2.
Inorg Chem ; 2020 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-32578989

RESUMO

Reaction of the Cu(I) sources, [Cu5](Mes)5 and [(iDipp)CuOtBu] (Mes = mesityl; iDipp = 1,3-bis(2,6-diisopropylphenyl)-1H-imidazol-2-ylidene) with the Zn(I) complex [Zn2](Cp*)2 leads to a mixture of intermetallic Cu/Zn clusters with a distribution of species that is dependent on the stoichiometric ratio of the reactants, the reaction time, as well as the temperature. Systematic and careful investigation of the product mixtures rendered the isolation of two new clusters possible, i.e., the Zn-rich, red cluster 1, [CuZn10](Cp*)7 = [Cu(ZnZnCp*)3(ZnCp*)4], as well as the Cu-rich, dark-green cluster 2 [Cu10Zn2](Mes)6(Cp*)2. Structure and bonding of these two species was rationalized with the help of density functional theory calculations. Whereas 1 can be viewed as an 18-electron Cu center coordinated to four ZnCp* and three ZnZnCp* one-electron ligands (with some interligand bonding interaction), compound 2 is better to be described as a six-electron superatom cluster. This unusual electron count is associated with a prolate distortion from a spherical superatom structure. This unexpected situation is likely to be associated with the ZnCp* capping units that offer the possibility to strongly bind to the top and the bottom of the cluster in addition to the bridging mesityl ligands stabilizing the Cu core of the cluster.

3.
Chemistry ; 2020 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-32378767

RESUMO

Although atomically precise polyhydrido copper nanoclusters are of prime interest for a variety of applications, they have so far remained scarce. Herein, this work describes the synthesis of a dithiophosphate-protected copper(I) hydride-rich nanocluster (NC), [Cu30 H18 {S2 P(OnPr)2 }12 ] (1H ), fully characterized by various spectroscopic methods and single-crystal X-ray diffraction. The X-ray structure of 1H reveals an unprecedented central Cu12 hollow icosahedron. Six faces of this icosahedron are capped by Cu3 triangles, the whole Cu30 core being wrapped by twelve dithiophosphate ligands and the whole cluster has ideal S6 symmetry. The locations of the 18 hydrides in 1H were ascertained by a single-crystal neutron diffraction study. They are composed of three types: capping µ3 -H, interstitial µ4 -H (seesaw) and µ5 -H ligands (square pyramidal), in good agreement with the DFT simulations. The numbers of hydrides and ligand resonances in the 1 H NMR spectrum of 1H are in line with their coordination environment in the solid state, retaining the S6 symmetry in solution. Furthermore, two new Se-protected polyhydrido copper nanoclusters, [Cu30 H18 {Se2 P(OR)2 }12 ] (2H : R=iPr 3H : R=iBu) were synthesized from their sulfur relative 1H via ligand displacement reaction and their X-ray structures feature the exceptional case where both the NC shape and size are fully conserved during the course of ligand exchange. DFT and TD-DFT calculations allow understanding the bonding and optical properties of clusters 1H -3H . In addition, the reaction of 1H with [Pd(PPh3 )2 Cl2 ] in the presence of terminal alkynes led to the formation of new bimetallic Cu-Pd alloy clusters [PdCu14 H2 {S2 P(OnPr)2 }6 (C≡CR)6 ] (4: R=Ph; 5: R=C6 H4 F).

4.
Chemistry ; 2020 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-32045497

RESUMO

The electronic structure of the spherical Mackay icosahedral nanosized cluster Pd55 (PiPr3 )12 (µ3 -CO)20 is analyzed by using DFT calculations. Results reveal that it can be considered as a regular superatom with a "magic" electron count of 20, characterized by a 1S2 1P6 1D10 2S2 jellium configuration. Its open shell nature is associated with partial occupation of non-jellium, 4d-type, levels located on the interior of the Pd55 kernel. This shows that the superatom model can be used to rationalize the bonding and stability of spherical ligated group 10 clusters, despite their apparent 0-electron count.

5.
Artigo em Inglês | MEDLINE | ID: mdl-32091662

RESUMO

Reported here is a readily available bis(imino)carbazole-based proligand that constitutes a convenient entry point into the challenging synthetic molecular chemistry of barium. It enables the preparation of rare or even, up to now, unknown, solution-stable heteroleptic barium complexes. The syntheses and structural features for the first molecular barium fluoride and the first barium stannylide, with an unsupported Ba-Sn bond, are described, along with other carbazolate barium species: an amide (both a remarkably stable starting material and an excellent hydrophosphination precatalyst), iodide, and silanylide. DFT analysis of bonding patterns in the barium stannylide and barium silanylide highlights a prevailingly ionic barium-tetrelide bond with a small covalent contribution.

6.
Inorg Chem ; 2020 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-31977197

RESUMO

Structurally precise copper hydrides [Cu11H2{S2P(OiPr)2}6(C≡CR)3], R = Ph (1), C6H4F (2), and C6H4OMe (3), were first synthesized from the polyhydrido copper cluster [Cu20H11{S2P(OiPr)2}9] with nine equivalents of terminal alkynes. Later, their isolated yields were significantly improved by direct synthesis from [Cu(CH3CN)4](PF6), [NH4][S2P(OiPr)2], NaBH4, and alkynes along with NEt3 in THF. 1, 2, and 3 were fully characterized by single-crystal X-ray diffraction, ESI-MS, and multinuclear NMR spectroscopy. All three clustershave 11 copper atoms, adopting 3,3,4,4,4-pentacapped trigonal prismatic geometry, with two hydrides inside the Cu11 cage, the position of which was ascertained by a single-crystal neutron diffraction structure of cluster 1 co-crystallized with a [Cu7(H){S2P(OiPr)2}6] (4) cluster. Six dithiophosphate and three alkynyl ligands stabilize the Cu11H2 core in which the two hydrides adopt a trigonal pyramidal coordination mode. This coordination mode is so far unprecedented for hydride. The 1H NMR resonance frequency of the two hydrides appears at 4.8 ppm, a value further confirmed by 2H NMR spectroscopy for their deuteride derivatives [Cu11(D)2{S2P(OiPr)2}6(C≡CR)3]. A DFT investigation allows understanding the bonding within this new type of copper(I) hydrides.

7.
J Am Chem Soc ; 141(33): 12957-12961, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31378060

RESUMO

Three bimetallic platinum/silver nanoclusters, PtAg20(dtp)12 (1), Pt2Ag33(dtp)17 (2), and Pt3Ag44(dtp)22 (3) (dtp: dipropyl dithiophosphate), with cluster electron counts of 8, 16, and 22, respectively, were produced via a one-phase coreduction method. Single-crystal X-ray structures reveal that their inner cores can be visualized as consisting of one, two, and three centered icosahedral Pt@Ag12 units, respectively. In 2 and 3, these units are vertex-sharing and are assembled linearly. Intriguingly, the 22-electron alloy (3) is isolobal to the linear triiodide anion, I3-, and represents the first example of a cluster made of three superatoms whose bonding characteristics are similar to those of a triatomic molecular species.

8.
Chemistry ; 25(59): 13509-13513, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31411764

RESUMO

The first unsupported barium siloxide, the homoleptic dimer [Ba2 {µ2 -OSi(SiMe3 )3 }3 {OSi(SiMe3 )3 }], is presented, and its structural features are discussed in the light of DFT computations. This complex, together with the related [Ba{µ2 -OSi(SiMe3 )3 }{N(SiMe3 )2 }]2 and their parent [Ba{N(SiMe3 )2 }2 ]2 , mediates the formation of asymmetric siloxanes R3 Si-O-SiR'3 through the first case of main group metal-mediated dehydrocoupling of silanols and hydrosilanes. Early kinetic analysis highlights an unusual catalytic manifold.

9.
Nanoscale ; 11(31): 14581-14586, 2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31359023

RESUMO

The synthesis, via a co-reduction method, of the first Pd-containing silver-rich 21-metal-atom nanocluster passivated by dithiolates, [PdAg20{S2P(OnPr)2}12] (1), is reported. 1 is an 8 electron superatom isoelectronic to [Ag21{S2P(OiPr)2}12]+. The doping of Pd in 1 leads to its high stability against degradation in solution and shows red emission in MeTHF at 77 K. In addition, we report the X-ray crystal structure of a multi-palladium doped silver nanocluster, [Pd6Ag14(S){S2P(OnPr)2}12] (2), for the first time. Its X-ray structure exhibits a sulfide-centered Pd6Ag2 rhombohedron surrounded by twelve additional silver atoms with S6 symmetry. The XPS study and DFT calculations indicate that 2 contains Pd(0) and Ag(i) metals. A significant decrease in the electrochemical gap was observed in the SWVs of 2.

10.
Phys Chem Chem Phys ; 21(16): 8428-8433, 2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30945710

RESUMO

DFT calculations were carried out on a series of tetrahedral 16-atom superatomic clusters having 20 or 18 jellium electrons (je) and structurally related to Au20, namely, [M16]4-/2- (M = Cu, Ag, and Au) and [M4'M12'']0/2+ (M' = Zn, Cd, Hg; M'' = Cu, Ag, Au). While the bare homonuclear 20-je species required further stabilization to be isolated, their 18-je counterparts exhibited better stability. Lowering the electron count led to structural modification from a compact structure (20-je) to a hollow sphere (18-je). Such a change could be potentially controlled by tuning redox properties. Among the 20-je heteronuclear [M4'M12''] neutral series, [Zn4Au12] appeared to meet the best stability criteria, but their 18-je relatives [M4'M12'']+, in particular [Zn4Cu12]2+ and [Cd4Au12]2+, offered better opportunities for obtaining stable species. Such species exhibit the smallest models for the M(111) surface of fcc metals, which expose designing rules towards novel high-dopant-ratio clusters as building blocks of nanostructured materials.

11.
Chemistry ; 25(37): 8854-8864, 2019 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-31026099

RESUMO

A set of calcium and barium complexes containing the fluoroarylamide N(C6 F5 )2 - is presented. These compounds illustrate the key role of stabilising M⋅⋅⋅F-C secondary interactions in the construction of low-coordinate alkaline earth complexes. The nature of Ca⋅⋅⋅F-C bonding in calcium complexes is examined in the light of structural data, bond valence sum (BVS) analysis and DFT computations. The molecular structures of [Ca{N(C6 F5 )2 }2 (Et2 O)2 ] (4'), [Ca{µ-N(SiMe3 )2 }{N(C6 F5 )2 }]2 (52 ), [Ba{µ-N(C6 F5 )2 }{N(C6 F5 )2 }⋅toluene]2 (62 ), [{BDIDiPP }CaN(C6 F5 )2 ]2 (72 ), [{N^NDiPP }CaN(C6 F5 )2 ]2 (82 ), and [Ca{µ-OB(CH(SiMe3 )2 )2 }{N(C6 F5 )2 }]2 (92 ), where {BDIDiPP }- and {N^NDiPP }- are the bidentate ligands CH[C(CH3 )NDipp]2 - and DippNC6 H4 CNDipp- (Dipp=2,6-iPr2 -C6 H3 ), are detailed. Complex 62 displays strong Ba⋅⋅⋅F-C contacts at around 2.85 Å. The calcium complexes feature also very short intramolecular Ca-F interatomic distances at around 2.50 Å. In addition, the three-coordinate complexes 72 and 82 form dinuclear structures due to intermolecular Ca⋅⋅⋅F-C contacts. BVS analysis shows that Ca⋅⋅⋅F-C interactions contribute to 15-20 % of the bonding pattern around calcium. Computations demonstrate that Ca⋅⋅⋅F-C bonding is mostly electrostatic, but also contains a non-negligible covalent contribution. They also suggest that Ca⋅⋅⋅F-C are the strongest amongst the range of weak Ca⋅⋅⋅X (X=F, H, Cπ ) secondary interactions, due to the high positive charge of Ca2+ which favours electrostatic interactions.

12.
Angew Chem Int Ed Engl ; 58(15): 4943-4947, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30770621

RESUMO

The structurally precise Cu-rich hydride nanoclusters [PdCu14 H2 (dtc/dtp)6 (C≡CPh)6 ] (dtc: di-butyldithiocarbamate (1); dtp: di-isopropyl dithiophosphate (2)) were synthesized from the reaction of polyhydrido copper clusters [Cu28 H15 (S2 CNn Bu2 )12 ]+ or [Cu20 H11 {S2 P(Oi Pr)2 }9 ] with phenyl acetylene in the presence of Pd(PPh3 )2 Cl2 . Their structures and compositions were determined by single-crystal X-ray diffraction and the results supported by ESI-mass spectrometry. Hydride positions in 1 were confirmed by single-crystal neutron diffraction. Each hydride is connected to one Pd0 and four CuI atoms in slightly distorted trigonalbipyramidal geometry. The anatomies of clusters 1 and 2 are very similar and DFT calculations allow rationalizing the interactions between the encapsulated [PdH2 ]2- unit and its Cu14 bicapped icosahedral cage. As a result, Pd has the highest coordination number (14) so far recorded.

13.
Chem Sci ; 9(33): 6785-6795, 2018 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-30310611

RESUMO

We have synthesized and structurally characterized a series of centred cuboctahedral copper clusters, namely [Cu13{S2CNR2}6{C[triple bond, length as m-dash]CR'}4](PF6), 1a-d (where a: R = n Bu, R' = CO2Me; b: R = n Bu, R' = CO2Et; c: R = iPr, R' = CO2Et; d: R = n Pr, R' = 3,5-(CF3)2C6H3); [Cu12(µ12-S){S2CNR2}6{C[triple bond, length as m-dash]CR'}4], 2a-c; [Cu12(µ12-Cl){S2CNR2}6{C[triple bond, length as m-dash]CR'}4](PF6), 3a-e (where e: R = n Bu, R' = Ph); [Cu12(µ12-Br){S2CN n Bu2}6{C[triple bond, length as m-dash]CPh}4](PF6), 4e; and [Cu12(µ12-Cl)(µ3-Cl){S2CN n Bu2}6{C[triple bond, length as m-dash]CCO2Me}3]+ 5a. Cluster 1a is the first structurally characterized copper cluster having a Cu13 centered cuboctahedral arrangement, a miniature of the bulk copper fcc structure. Furthermore, the partial Cu(0) character in the 2-electron superatoms 1 was confirmed by XANES. Inverse coordination clusters 2-5 are the first examples of copper clusters containing main group elements (Cl, Br, S) with a hyper-coordination number, twelve. A combined theoretical and experimental study was performed, which shows that the central copper (formally Cu1-) in nanoclusters 1 can be replaced by chalcogen/halogen atoms, resulting in the formation of clusters 2-5 which show enhanced luminescence properties and increase in the ionic component of the host-guest interaction as Br ≈ Cl > S > Cu, which is consistent with the Cu-X Wiberg indices. The new compounds have been characterized by ESI-MS, 1H, 13C NMR, IR, UV-visible, emission spectroscopy, and the structures 2a-b, 3d-e, 4e and 5a were established by X-ray diffraction analysis.

14.
Acc Chem Res ; 51(10): 2475-2483, 2018 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-30264984

RESUMO

The chalcogenolato silver and copper superatoms are currently a topic of cutting edge research besides the extensively studied Au n(SR) m clusters. Crystal structure analysis is an indispensable tool to gain deep insights into the anatomy of these sub-nanometer clusters. The metal framework and spatial arrangement of the chalcogenolates around the metal core assist in unravelling the structure-property relationships and fundamental mechanisms involved in their fabrication. In this Account, we discuss our contribution toward the development of dichalcogenolato Ag and Cu cluster chemistry covering their fabrication and precise molecular structures. Briefly introducing the significance of the single crystal structures of the atomically precise clusters, the novel dichalcogenolated two-electron superatomic copper and its alloy systems are presented first. The [Cu13{S2CNR}6{C≡CR'}4]+ is so far the first unique copper cluster having Cu13 centered cuboctahedra, which is a miniature of bulk fcc structure. The galvanic exchange of the central Cu with Ag or Au results in a similar anatomy of formed bimetallic [Au/Ag@Cu12(S2CN nBu2)6(C≡CPh)4][CuCl2] species. This is unique in the sense that other contemporary M13 cores in group 11 superatomic chemistry are compact icosahedra. The central doping of Ag or Au significantly affects the physiochemical properties of the bimetallic Cu-rich clusters. It is manifested in the dramatic quantum yield enhancement of the doped species [Au@Cu12(S2CN nBu2)6(C≡CPh)4]+ with a value of 0.59 at 77 K in 2-MeTHF. In the second part, the novel eight-electron dithiophosphate- and diselenophosphate-protected silver systems are presented. A completely different type of architecture was revealed for the first time from the successful structural determination of [Ag21{S2P(O iPr)2}12]+, [Ag20{S2P(O iPr)2}12] and [Au@Ag19{S2P(OPr)2}12]. They exhibit a nonhollow M13 (Ag or AuAg12) icosahedron, capped by 8 and 7 Ag atoms in the former and latter two species, respectively. The overall metal core units are protected by 12 dithiophosphate ligands and the metal-ligand interface structure was found to be quite different from that of Au n(SR) m. Notably, the [Ag20{S2P(O iPr)}12] cluster provides the first structural evidence of a silver superatom with a chiral metallic core. This chirality arises through the simple removal of one of capping Ag+ cations of [Ag21{S2P(O iPr)2}12]+ present on its C3 axis. Further, the effects of the ligand exchange on the structures of [Ag20{Se2P(O iPr)2}12], [Ag21{Se2P(OEt)2}12]+, and [AuAg20{Se2P(OEt)2}12]+ are studied extensively. The structure of the former species is similar to its dithiophosphate counterpart ( C3 symmetry). The latter two ( T symmetry) differ in the arrangement of 8 capping Ag atoms, as they form a cube engraving the Ag13 (AuAg12) icosahedron. The blue shifts in absorption spectra and photoluminescence further indicate the strong influence of the central Au atom in the doped clusters. Finally, the first paradigm of unusual heteroatom doping induced size-structure transformations is discussed by presenting the case of formation of [Au3Ag18{Se2P(O iPr)2}12]+ upon Au doping into [Ag20{Se2P(O iPr)2}12]0. Finally, before concluding this Account, we discuss the possibility of many unique structural isomers with different physical properties for the aforementioned Ag superatoms which need to be explored extensively in the future.

15.
Angew Chem Int Ed Engl ; 57(44): 14630-14634, 2018 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-29981271

RESUMO

The paramagnetic cluster [Cu43 Al12 ](Cp*)12 was obtained from the reaction of [CuMes]5 and [AlCp*]4 (Cp*=η5 -C5 Me5 ; Mes=mesityl). This all-hydrocarbon ligand-stabilized M55 magic atom-number cluster features a Mackay-type nested icosahedral structure. Its open-shell 67-electron superatom configuration is unique. Three unpaired electrons occupy weakly antibonding jellium states. The situation prefigures the formation of a conduction band, which is in line with the measured temperature-independent magnetism. Steric protection by twelve Cp* ligands suppresses the intrinsic polyradicalar reactivity of the Cu43 Al12 core.

16.
Chemistry ; 24(54): 14352-14357, 2018 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-29968945

RESUMO

A templated galvanic exchange performed on [Ag20 {Se2 P(OiPr)2 }12 ] of C3 symmetry with three equiv AuI yields a mixture of [Au1+x Ag20-x {Se2 P(OiPr)2 }12 ]+ (x=0-2) from which [Au@Ag20 {Se2 P(OiPr)2 }12 ]+ and [Au@Au2 Ag18 {Se2 P(OiPr)2 }12 ]+ are successfully characterized to have T and C1 symmetry, respectively. Crystal structural analyses combined with DFT calculations on the model compounds explicitly demonstrate that the central Ag0 of Ag20 being oxidized by AuI migrates to the protecting atomic shell as a new capping AgI , and both second and third Au dopants prefer occupying non-adjacent icosahedron vertices. The differences in symmetry, T and C1 , are manifested in the spatial orientation of their protecting atomic shell composed of eight capping Ag atoms as well as re-construction upon the replacement of Ag atoms on the vertices of AuAg12 icosahedral core with second and third Au dopants. As a result, a unique pathway for substitutional-doped clusters with increased nuclearity is proposed.

17.
Chemphyschem ; 2018 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-29697900

RESUMO

Exploring the versatility of atomically precise clusters is a relevant issue in the design of functional nanostructures. Superatomic clusters offer an ideal framework to gain further understanding of the different distinctive size-dependent physical and chemical properties. Here, we propose [Au12 (SR)6 ]2- as a minimal 8-electron superatom related to the prototypical [Au25 (SR)18 ]- cluster, depicting half of its core-mass (2.3 kDa vs 5.0 kDa). The [Au12 (SMe)6 ]2- cluster fulfills a 1S2 1P6 electronic configuration, with a distorted tetrahedral Au8 core further viewed as an SP3 -hybridized superatom. The distinctive optical properties show a blue-shift for the first relevant 1P→1D transition, in comparison to [Au25 (SR)18 ]- . In addition, chiroptical activity is observed, denoting intrinsic core chirality. We expect that our results can shed light into the variation of the molecular properties according to the size-dependent properties, and serve as guidelines for further experimental exploration of minimal or ultrasmall nanoclusters.

18.
Nanoscale ; 10(15): 6855-6860, 2018 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-29616252

RESUMO

Controlling the metal nanoclusters with atomic precision is highly difficult and further studies on their transformation reactions are even more challenging. Herein we report the controlled formation of a silver alloy nanocluster [AuAg19{S2P(OnPr)2}12] (1) from an Ag20 template via a galvanic exchange route. X-ray structural analysis reveals that the alloy structure comprises of a gold-centered Ag12 icosahedron, Au@Ag12, capped by seven silver atoms. Interestingly upon reacting with one equiv. of silver(i) salt, (1) can transform into a higher nuclearity nanocluster, [Au@Ag20{S2P(OnPr)2}12]+ (2). The conversion process is studied via ESI mass spectrometry and 31P NMR spectroscopy. This kind of size-structural transformation at the single atom level is quite remarkable. Furthermore, the compositions of all the doped nanoclusters (1, 2) were fully characterized with ESI-MS and EDS. The blue shift depicted in the UV-visible and emission spectra of the doped nanoclusters (1, 2) compared with the precursor, Ag20, demonstrates that the doping atoms have significant effects on the electronic structures.

19.
Inorg Chem ; 57(8): 4328-4339, 2018 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-29620359

RESUMO

Luminescent materials based on copper complexes are currently receiving increasing attention because of their rich photophysical properties, opening a wide field of applications. The copper iodide clusters formulated [Cu4I4L4] (L = ligand), are particularly relevant for the development of multifunctional materials based on their luminescence stimuli-responsive properties. In this context, controlling and modulating their photophysical properties is crucial and this can only be achieved by thorough understanding of the origin of the optical properties. We thus report here, the comparative study of a series of cubane copper iodide clusters coordinated by different phosphine ligands, with the goal of analyzing the effect of the ligands nature on the photoluminescence properties. The synthesis, structural, and photophysical characterizations along with theoretical investigations of copper iodide clusters with ligands presenting different electronic properties, are described. A method to simplify the analysis of the 31P solid-state NMR spectra is also reported. While clusters with electron-donating groups present classical luminescence properties, the cluster bearing strong electron-withdrawing substituents exhibits original behavior demonstrating a clear influence of the ligands properties. In particular, the electron-withdrawing character induces a decrease in energy of the unoccupied molecular orbitals, that consequently impacts the emission properties. The modification of the luminescence thermochromic properties of the clusters are supported by density functional theory (DFT) calculations. This study demonstrates that the control of the luminescence properties of these compounds can be achieved through modification of the coordinated ligands, nevertheless the role of the crystal packing should not be underestimated.

20.
Dalton Trans ; 47(11): 3965-3975, 2018 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-29464264

RESUMO

The present work describes the one-pot synthesis and electrochemical, photophysical and second-order nonlinear optical (NLO) properties of a series of dipolar π-delocalized Ru(ii) dialkynyl complexes. The eight new asymmetrical D-π-Ru-π-A push-pull chromophores incorporate pyranylidene ligands as pro-aromatic donor groups (D) and formaldehyde, indane-1,3-dione, pyrimidine or pyrimidinium as electron-attracting groups (A) separated by ruthenium bis-acetylide fragments and π-conjugated linkers. The second-order nonlinear optical (NLO) properties of all eight complexes were determined by the Electric-Field-Induced Second Harmonic generation (EFISH) technique (operating at 1907 nm), and were compared to those of their purely organic analogs. All investigated compounds (organic and organometallic) exhibited positive µß values, which dramatically increased for the complexes due to the presence of ruthenium in the π-conjugated core. The second-order NLO response could also be easily modulated by changing the nature of alkynyl substituents. The most promising ruthenium complexes 7 and 8 of the series with the pyrimidinium fragment displayed µß values of 14 000 × 10-48 esu. The effect of structural modifications on the redox and spectroscopic properties of the complexes was also studied. The intramolecular charge transfer (ICT) occurring through the ruthenium center of the push-pull σ-dialkynyl complexes was investigated by combining experimental and theoretical data.

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