Smallest Optical Gap for Pt(II)-Pt(IV) Mixed-Valence Pt-Cl and Pt-Br Chain Complexes Achieved by Using a Multiple-Hydrogen-Bond Approach

Hexagonal crystalline Magnus' green salt analogues prepared from hydroxy-functionalised Pt and Pd complexes

New Magnus' green salt (MGS) analogues, [M(dabdOH)2][MCl4]·2H2O (dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol; M = Pd (1) and M = Pt(2)), in which [M(dabdOH)2]2+ and [MCl4]2- are stacked alternately to form linear chains, were obtained as hexagonal plate crystals. The hexagonal shape and large crystal size are unprecedented features as MGS analogues. An unusual trigonal grade separation of chain complexes has been revealed by the structural analysis. 1 and 2 exhibited remarkable yellow and pink colours, respectively, which are derived from weak M⋯M interactions. The dabdOH ligand, which has an additional hydrogen donor group (hydroxy group), produces a multiple-hydrogen-bond network. The combination of intrachain and interchain hydrogen bonds gives a two-dimensional (2D) hydrogen-bond sheet, and each 2D sheet is indirectly connected by hydrogen bonds via lattice water molecules. The OH-functionalised ligand greatly increases the hydrophilicity of the MGS analogues and yields the largest single crystals of all MGS analogues reported so far. The trigonal grade-separated chain structure is likely due to the geometric matching between the periodicity of chains and the short axis width of the chain. This strategy opens up new insight for preparing large crystals of MGS analogues and for constructing trigonal grade-separated nanowires in molecular crystals.

Porous Mn2+ Magnet with a Pt-Cl Framework: Correlation between Water Vapor Adsorption/Desorption and Slow Magnetic Relaxation

We report the water adsorption/desorption behavior and dynamic magnetic properties of the Pt-Cl chain complex [{[Pt(en)₂ ][PtCl₂ (en)₂ ]}₃ ][{(MnCl₅ )Cl₃ }₂ ] ⋅ 12H₂ O (1). Upon heating 1 in a vacuum, we obtained the dehydrated form [{[Pt(en)₂ ][PtCl₂ (en)₂ ]}₃ ][{(MnCl₅ )Cl₃ }₂ ] (1DH). The framework structures of 1 and 1DH are identical, and both complexes underwent slow magnetic relaxation. However, the magnetic relaxation times for 1DH were shorter than those for 1, meaning that the dynamic magnetic properties were controlled upon water vapor adsorption/desorption. From detailed analyses of the dynamic magnetic behavior, a phonon-bottleneck effect contributes to the magnetic relaxation processes. We discuss the mechanism for the changes in the magnetic relaxation processes upon dehydration in terms of the heat capacity and thermal conductivity.

Ni(III) Mott-Hubbard-like State Containing High-Spin Ni(II) in a Semiconductive Bromide-Bridged Ni-Chain Compound

Halogen-bridged linear chain metal complexes (MX-Chains) are fascinating compounds that have a quasi-one-dimensional (1D) electronic system. In this study, we synthesized the first Ni-based MX-Chain compound having hydroxy groups, i.e., [Ni(dabdOH)₂Br]Br₂·[Ni(dabdOH_x)₂Br]_0.5·(2-PrOH)_0.25·(MeOH)_0.25 (1·solvent, x = ∼0.6, dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol). Single-crystal X-ray diffraction revealed that the MX-Chains in 1·solvent formed sheets and single-chain structures in the superlattice. It suggested an MH-like state, whereas the polarized reflection and Raman spectra suggested a CDW-like state. Magnetic and electron spin resonance measurements revealed that both high-spin Ni(II) (∼15%) and low-spin Ni(III) (∼85%) sites are present in the chain structures, i.e., the metal sites show mixed valency. Therefore, we concluded that 1·solvent adopts an intermediate state between the MH and CDW states. Moreover, a single crystal of 1·solvent exhibited semiconductive characteristics along the chain direction. This finding represents a new structural and electronic state of 1D electronic systems as well as MX-Chains.

Chiral Hybrid Copper(I) Halides for High Efficiency Second Harmonic Generation with a Broadband Transparency Window

Chiral hybrid organic-inorganic metal halides (HOMHs) with intrinsic noncentrosymmetry have shown great promise for applications in second-order nonlinear optics (NLO). However, established chiral HOMHs often suffer from their relatively small band gaps, which lead to negative impacts on transparent window and laser-induced damage thresholds (LDT). Here, we have synthesized two chiral HOMHs based on Cu^I halides, namely (R-/S-MBA)CuBr₂ , which feature well-balanced NLO performances with a highly efficient SHG response, outstanding optical transparency, and high LDT. The effective second-order NLO coefficient of (R-MBA)CuBr₂ has been determined to be ≈24.7 pm V^-1 , which is two orders of magnitude higher than that of their Cu^II counterparts. This work shows the promising potential of Cu^I -based chiral HOMHs for nonlinear photonic applications in wide wavelength regions.

Elucidating 2D Charge-Density-Wave atomic structure in an MX-chain by the 3D-ΔPair Distribution Function method

Many solids, particularly low-dimensional systems, exhibit charge density waves (CDWs). In one dimension, charge density waves are well understood, but in two dimensions, their structure and their origin are difficult to reveal. Here, the 2D Charge-Density-Wave atomic structure and stabilization mechanism in the bromide-bridged Pd compound [Pd(cptn) 2 Br]Br 2 (cptn = 1 R ,2 R -diaminocyclopentane) is investigated by means of single-crystal X-ray diffraction employing the 3D-ΔPair Distribution Function (3D-ΔPDF) method. Analysis of the diffuse scattering using 3D-ΔPDF shows that a 2D-CDW is stabilized by a hydrogen-bonding network between Br - counteranion and the amine (NH 2 ) group of the cptn in-plane ligand, and that 3D ordering is prevented due to a weak plane to plane correlation. We extract the effective displacements of the atoms describing the atomic structure quantitatively and discuss the stabilization mechanism of the 2D-CDW. Our study provides a method to identify and measure the key interaction responsible for the dimensionality and stability of the CDW that can help further progress of rational design.

Interdigitated Pt-Br chains with π-stacking: an approach toward Robin-Day class I mixed valency in MX-chain complexes

The first interdigitated MX-type chain complex with infinite π-stacked arrays was synthesized. The synchronization between a Pt-Br⋯ chain and π-stacking periodicities led to the longest M-X-M distance (6.6978(15) Å) and nil or negligible intervalence charge transfer, which is essential to realize the Robin-Day class I mixed valence state in MX chains.

An unusual Pd(III) oxidation state in the Pd-Cl chain complex with high thermal stability and electrical conductivity

The Pd(iii) oxidation state is unusual and unstable since it strongly tends to disproportionate. We synthesized the quasi-one-dimensional (1D) halogen-bridged Pd(iii)-Cl complex [Pd(dabdOH)2Cl]Cl2 (1-Cl; dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol) with multiple hydrogen bonds. From single-crystal X-ray diffraction, the bridging Cl- ions were located at the midpoint of the Pd-Cl-Pd moieties in the 1D chains, indicating that the Pd ions are in a Pd(iii) average valence (AV) state. Moreover, bright spots for the Pd(iii) dz2 orbitals in the upper Hubbard band above the Fermi level were observed every ∼5 Å using scanning tunnelling microscopy. These results clearly indicate that the Pd ions are in a Pd(iii) AV state in 1-Cl. In addition, 1-Cl has the highest thermal stability (470 K) among the Pd(iii) complexes reported and the highest electrical conductivity (0.6 S cm-1 at 300 K) among the 1D Pd-Cl chains reported so far.

Modulating the ferroelectric performance by altering halogen anions in the crystals of tetranuclear copper-clusters

The ferroelectric performance of tetranuclear copper clusters can be modulated by altering the free halogen anions existing in the crystal structure.

Conductive zigzag Pd(iii)–Br chain complex realized by a multiple-hydrogen-bond approach

Coexistence of zigzag structure and the uncommon Pd(iii) oxidation state in quasi-1D halogen-bridged metal complexes was realized in a conductive Br-bridged Pd chain complex, [Pd(dabdOH)₂Br]SO₄·3H₂O (2), for the first time.

MX-type single chain complexes with an aromatic in-plane ligand: incorporation of aromatic interactions for stabilizing the chain structure

MX-type one-dimensional complexes [Pt^IV(amp)₂Br₂][Pt^II/IV(amp)₂Br]₂(HSO₄)₂(SO₄)₂·13H₂O (3) and [Pt^IV(amp)₂Br₂][Pt^II/IV(amp)₂Br]₂(H₂PO₄)₆·8H₂O (4) were synthesized as the first analogue containing only an aromatic in-plane ligand. The Pt-Br chain structures of 3 and 4 are stabilized by both the hydrogen-bond network along the chain and the π-stacking via intercalated Pt(iv) complexes. Structural and spectroscopic studies indicated that both 3 and 4 form the Pt(ii/iv) mixed valence state.