Assembly of a heterometallic polynuclear Sn(IV)-Cu(I) cluster based on Sn(edt)2 (edt = ethane-1,2-dithiolate) as a metalloligand

Near-Infrared Luminescence in Trinuclear Mixed-Metal Chalcogenolate Complexes of the Types [M2Ti(EPh)6(PPh3)2] (M = Cu, Ag; E = S, Se) and [Na(thf)3]2[Ti(SPh)6]

The optical properties of four new trinuclear chalcogenolato bridged metal complexes [Ag₂Ti(SPh)₆(PPh₃)₂], [Na(thf)₃]₂[Ti(SPh)₆], [Cu₂Ti(SePh)₆(PPh₃)₂], and [Ag₂Ti(SePh)₆(PPh₃)₂] have been investigated by absorption and photoluminescence spectroscopy as well as time-dependent density functional theory (TDDFT) calculations and compared to the results published recently for [Cu₂Ti(SPh)₆(PPh₃)₂]. All of these compounds are distinguished by efficient near-infrared luminescence at ∼880-1200 nm in the solid state at low temperatures, which remains quite intense for the copper-titanium complexes at ambient temperature with PL quantum yields of 9.5 and 4.8% at λ_PL = 1090 and 1240 nm for [Cu₂Ti(EPh)₆(PPh₃)₂], E = S, Se, respectively. According to the calculations, a peculiar feature of the lowest-energy electronic transitions in these complexes is their high localization on the metal and chalcogen atoms, with negligible contributions of the "external" ligand groups. Correspondingly, the type of atoms in the M₂TiE₆ (M = Cu, Ag, Na) core structure determines optical properties such as the absorption and emission wavelengths and PL lifetime.

Optical properties of trinuclear metal chalcogenolate complexes - room temperature NIR fluorescence in [Cu2Ti(SPh)6(PPh3)2]

The optical properties of four isostructural trinuclear chalcogenolato bridged metal complexes [Cu₂Sn(SPh)₆(PPh₃)₂], [Cu₂Sn(SePh)₆(PPh₃)₂], [Ag₂Sn(SPh)₆(PPh₃)₂] and [Cu₂Ti(SPh)₆(PPh₃)₂] have been investigated by absorption and photoluminescence spectroscopy and time-dependent density functional theory (TDDFT) calculations. All copper-tin compounds demonstrate near-infrared (NIR) phosphorescence at ∼900-1100 nm in the solid state at low temperature, which is nearly absent at ambient temperature. Stokes shifts of these emissions are found to be unusually large with values of about 1.5 eV. The copper-titanium complex [Cu₂Ti(SPh)₆(PPh₃)₂] also shows luminescence in the NIR at 1090 nm but with a much faster decay (τ ∼ 10 ns at 150 K) and a much smaller Stokes shift (ca. 0.3 eV). Even at 295 K this fluorescence is found to comprise a quantum yield as high as 9.5%. The experimental electronic absorption spectra well correspond to the spectra simulated from the calculated singlet transitions. In line with the large Stokes shifts of the emission spectra the calculations reveal for the copper-tin complexes strong structural relaxation of the excited triplet states whereas those effects are found to be much smaller in the case of the copper-titanium complex.

Localized Surface Plasmon Resonance in Semiconductor Nanocrystals

Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals (NCs) that results in resonant absorption, scattering, and near field enhancement around the NC can be tuned across a wide optical spectral range from visible to far-infrared by synthetically varying doping level, and post synthetically via chemical oxidation and reduction, photochemical control, and electrochemical control. In this review, we will discuss the fundamental electromagnetic dynamics governing light matter interaction in plasmonic semiconductor NCs and the realization of various distinctive physical properties made possible by the advancement of colloidal synthesis routes to such NCs. Here, we will illustrate how free carrier dielectric properties are induced in various semiconductor materials including metal oxides, metal chalcogenides, metal nitrides, silicon, and other materials. We will highlight the applicability and limitations of the Drude model as applied to semiconductors considering the complex band structures and crystal structures that predominate and quantum effects that emerge at nonclassical sizes. We will also emphasize the impact of dopant hybridization with bands of the host lattice as well as the interplay of shape and crystal structure in determining the LSPR characteristics of semiconductor NCs. To illustrate the discussion regarding both physical and synthetic aspects of LSPR-active NCs, we will focus on metal oxides with substantial consideration also of copper chalcogenide NCs, with select examples drawn from the literature on other doped semiconductor materials. Furthermore, we will discuss the promise that LSPR in doped semiconductor NCs holds for a wide range of applications such as infrared spectroscopy, energy-saving technologies like smart windows and waste heat management, biomedical applications including therapy and imaging, and optical applications like two photon upconversion, enhanced luminesence, and infrared metasurfaces.

Shape Control of Colloidal Cu2-x S Polyhedral Nanocrystals by Tuning the Nucleation Rates

Synthesis protocols for colloidal nanocrystals (NCs) with narrow size and shape distributions are of particular interest for the successful implementation of these nanocrystals into devices. Moreover, the preparation of NCs with well-defined crystal phases is of key importance. In this work, we show that Sn(IV)-thiolate complexes formed in situ strongly influence the nucleation and growth rates of colloidal Cu_2-x S polyhedral NCs, thereby dictating their final size, shape, and crystal structure. This allowed us to successfully synthesize hexagonal bifrustums and hexagonal bipyramid NCs with low-chalcocite crystal structure, and hexagonal nanoplatelets with various thicknesses and aspect ratios with the djurleite crystal structure, by solely varying the concentration of Sn(IV)-additives (namely, SnBr₄) in the reaction medium. Solution and solid-state ¹¹⁹Sn NMR measurements show that SnBr₄ is converted in situ to Sn(IV)-thiolate complexes, which increase the Cu_2-x S nucleation barrier without affecting the precursor conversion rates. This influences both the nucleation and growth rates in a concentration-dependent fashion and leads to a better separation between nucleation and growth. Our approach of tuning the nucleation and growth rates with in situ-generated Sn-thiolate complexes might have a more general impact due to the availability of various metal-thiolate complexes, possibly resulting in polyhedral NCs of a wide variety of metal-sulfide compositions.

A novel heterometallic dinuclear compound: rac-pentaaqua-1κ5O-(μ-2-sulfidoacetato-1:2κ3O:O',S)bis(2-sulfidoacetato-2κ2O,S)manganese(II)tin(IV)

The title racemic heterometallic dinuclear compound, [MnSn(C(2)H(2)O(2)S)(3)(H(2)O)(5)], (I), contains one main group Sn(IV) metal centre and one transition metal Mn(II) centre, and, by design, links the Mn(II) centre to the building unit of the (Δ/Λ) [SnL(3)](2-) complex anion (L is the 2-sulfidoacetate dianion). In this cluster, the Sn(IV) centre of the (Δ/Λ) [SnL(3)](2-) unit is coordinated by three O atoms and three S atoms from three L ligands to form an [SnO(3)S(3)] octahedral coordination environment. The Mn(II) centre is in an [MnO(6)] octahedral coordination environment, with five O atoms from five water molecules and the sixth from the μ(2)-L ligand of the (Δ/Λ) [SnL(3)](2-) unit. Between adjacent dinuclear molecules, there are many hydrogen-bond interactions of O-H···O, O-H···S, C-H···O and C-H···S types. Of these, eight pairs of O-H...O hydrogen bonds fuse all the dinuclear molecules into two-dimensional supramolecular sheets along the bc plane. Adjacent supramolecular sheets are further connected through O-H···S hydrogen bonds to give a three-dimensional supramolecular network.

Self-assembly of luminescent Sn(IV)/Cu/S clusters using metal thiolates as metalloligands

Through the use of (Bu4N)2[Sn3S4(edt)3] (edt=SCH2CH2S(2-)) and Sn(SPh)4 as metalloligands, three neutral compounds have been obtained: [(Ph3P) 2Cu] 2SnS(edt)(2).2CH2Cl2.H2O (1a), [(Ph3P) 2Cu]2SnS(edt)2.2DMF.H2O (1b), and [(Ph3P)Cu] 2Sn(SPh)(6).3H 2O (2). Single-crystal X-ray diffraction studies revealed that compounds 1a and 1b contain the same neutral butterfly-like [(Ph3P)2Cu]2SnS(edt)2 cluster, which consists of one central SnS 5 dreich trigonal bipyramid sharing one vertex and two sides with two slightly distorted CuS 2P2 tetrahedrons. Compound 2 has a linear [(Ph3P)Cu]2Sn(SPh)6 cluster that is composed of a central distorted SnS 6 octahedron sharing two opposite planes with two slightly distorted CuS 3P tetrahedrons. Compound 1a exhibited an emission at 568 nm (tau=12.86 micros) in the solid state, while in CH 2Cl 2 solution, 1a exhibited a green emission at 534 nm (tau=4.75 micros). Compound 2 showed an intense red emission at 696 nm (tau=3.64 micros) upon excitation at 307 nm in the solid state.

A Rare Chiral Self-Catenated Network Formed by Two Cationic and One Anionic Frameworks

A chiral heterometallic complex, obtained from the solvothermal reaction of [Zn(4-pytpy)2](BF4)2 [4-pytpy=4'-(4-pyridyl)-2,2':6',2''-terpyridine] and CuCN, exhibits a rare self-catenated network formed by two 3D cationic and one 3D anionic frameworks.