When nanoparticles become small (ca. <5 nm), surface stress becomes significant and generates strain that results in a change of surface structures. In this regard, the surface lattice of nanoparticles can be engineered to create strains or other structural changes with atomic positions away from the normal lattice points. Such changes impact the electronic and catalytic properties of nanoparticles. Recently, several groups have reported the change of catalytic and electrocatalytic properties of bimetallic nanoparticles. In this tutorial review, we discuss the principles related to lattice strain and other distorted structures, and the catalytic properties of bimetallic nanostructures.

A new motif for infinite metal atom wires with tunable compositions and properties is developed based on the connection between metal paddlewheel and square planar complex moieties. Two infinite Pd chain compounds, [Pd4(CO)4(OAc)4Pd(acac)2] 1 and [Pd4(CO)4(TFA)4Pd(acac)2] 2, and an infinite Pd-Pt heterometallic chain compound, [Pd4(CO)4(OAc)4Pt(acac)2] 3, are identified by single-crystal X-ray diffraction analysis. In these new structures, the paddlewheel moiety is a Pd four-membered ring coordinated by bridging carboxylic ligands and μ2 carbonyl ligands. The planar moiety is either Pd(acac)2 or Pt(acac)2 (acac = acetylacetonate). These moieties are connected by metallophilic interactions. The results showed that these one-dimensional metal wire compounds have photoluminescent properties that are tunable by changing ligands and metal ions. 3 can also serve as a single source precursor for making Pd4Pt bimetallic nanostructures with precise control of metal composition.

A new motif for infinite metal atom wires with tunable compositions and properties is developed based on the connection between metal paddlewheel and square planar complex moieties. Two infinite Pd chain compounds, [Pd 4 (CO) One-dimensional infinite metal-metal-bond compounds, [1] also known as metal atom wires, or metal atom chain complexes, have attracted much attention for their potential electronic, [2] magnetic, [3] and photoluminescent [4] applications. So far, the majority of such compounds reported are entirely composed of the linear chain motif, which has been demonstrated in the infinite one-dimensional (1D) metal chain compounds of Au, [4b, c] Pt, [5] Pd, [2a, 3a, 6] Ru, [7] Rh, [2b, c, 8] and other heterometallic chain complexes, [2d, 4a, 9] with few exceptions.[10]As shown in Scheme 1, two types of commonly known linear chain motifs are square-planar (Scheme 1 a) and paddlewheel (Scheme 1 b) metal complexes. [11] For the former, the coordinated ligands need to form a coplanar configuration; thus small ligands, such as NH 3 , and large ligands, such as acetylacetonate (acac) and maleonitriledithiolate (mnt), are suitable. For the paddlewheel molecules, bridging ligands, such as acetate (OAc), amide and biimidazole, are necessary components.[12] When they are connected together, the above moieties align in either a nearly straight or a zigzag line. However, other types of motif for infinite metal chain structures are still very rare.Herein, we demonstrate a new motif (Scheme 1 c) for metal atom wires using both square-planar and four-membered paddlewheel units. Unlike the previously reported linear chains, this new motif is composed of both a paddlewheel ring and a coplanar configured complex, and the direction of the infinite chain is at an angle with respect to the longest M À M linear unit. We demonstrate that, using this new motif, both homometallic (Pd À Pd) and heterometallic (Pd À Pt) atom wires can be generated by controlling the types of ligands used. This structural flexibility makes it possible to design 1D infinite metal-metal bond compounds with tunable electronic band gaps.The three types of metal atom chain complexes described herein are [Pd 4 (CO) ]/CO system. This method of reacting metal acetylacetonate salt with CO and acetic acid can also be applied to prepare a Pd À Pt heterometallic chain complex 3, following a similar procedure using both [Pd(acac) 2 ] and [Pt(acac) 2 ]. Scheme 2 shows the synthetic route for 1, and the experimental details are described in the Supporting Information. Scheme 1. Motifs for infinite metal chain compounds. Linear type motif composed of a) square-planar and b) paddlewheel molecules. c) New motif described herein.

Surface Lattice-Engineered Bimetallic Nanoparticles and Their Catalytic Properties -[89 refs.]. -(WU, J.; LI, P.; PAN, Y.-T.; WARREN, S.; YIN, X.; YANG*, H.; Chem. Soc. Rev. 41 (2012) 24, 8066-8074, http://dx.doi.org/10.1039/c2cs35189g ; Dep. Chem. Biomol. Eng., Univ. Ill., Urbana, IL 61801, USA; Eng.) -Schramke 13-200