On the tuning of electric conductance of extended metal atom chains via axial ligands for [Ru3(μ3-dpa)4(X)2]0/+ (X = NCS−, CN−)

Abstract

The influence of a pi-acid cyanide axial ligand on the metal-metal interactions of [Ru(3)(mu(3)-dpa)(4)(X)(2)](0/+) (X = NCS(-), CN(-)) is manifested by the measurements of single-molecule conductance coupled with in situ electrochemical control.

Metal–metal interactions in linear tri-, penta-, hepta-, and nona-nuclear ruthenium string complexes

“…The trend for the Ru-Ru distances is the same in our molecular calculations as in the X-ray data, showing that Cl − as the axial ligand causes the shortest Ru-Ru distances, while CN − leads to the longest Ru-Ru distances. A similar trend in Ru-Ru distances was also obtained in a previous computational study of Ru 3 (dpa) 4 X 2 (X = Cl − , CN − ) [33], and X = ( NCS − ) [27]. The longer Ru-Ru distance for X = CN − was explained as originating from the better ability of the cyanide ligand to form a π backbonding interaction with the ruthenium centers, therefore reducing the strength of the metal-metal interaction.…”

“…All of the complexes were calculated in singlet state in order to facilitate comparison of the different models with different lengths and axial ligands. Since the experimentally obtained spin states for Ru 3 complexes have been found to vary with the nature of the axial ligands [27,33], we optimized the spin state for the trimetallic complexes. Triplet ground state was predicted for all the Ru 3 complexes regardless of axial ligand.…”

“…Axial ligands (X in Fig. 1a) vary from small anions, such as Cl − , CN − , and NCS − to larger arylacetylide ligands [27]. Overall, the versatile ligand structure provides an easy tool for tuning the structures.…”

“…Metal string complexes provide a promising approach for the creation of nano-scale electrical wires [1]. The electric conductivity of metal string complexes correlates qualitatively with the strength of the metal-metal interaction in the complex, and can be tuned by the choice of transition metal, its oxidation state, and the ligands used [27]. Metal string complexes also have interesting magnetic properties, such as the spin-crossover behavior of [Co 3 (dpa) 4 Cl 2 ] + [9,31].…”

“…Later, a synthesis with a better yield [33] and triruthenium metal string complexes with different axial ligands [27,33,34] were reported. Moreover, it was noted that the terminal ligands affected the electronic configurations on triruthenium metal string complexes, causing, for example, a singlet state in [Ru 3 (dpa) 4 Cl 2 ] and a triplet state in [Ru 3 (dpa) 4 (CN) 2 ] [33].…”