Pentanuclear Heterometallic String Complexes with High‐Bond‐order Units [Ni23+−Mo24+−Ni2+(bna)4X2]3+ (X = Cl, NCS)

Neutral [X‐{Ir2}‐{Ir2}‐X] (X = Cl, Br, SCN, I) and dicationic [L‐{Ir2}‐{Ir2}‐L]2+ (L = MeCN, Me2CO) tetrametallic iridium chains made by connecting two dinuclear {Ir2} units ({Ir2} = [Ir2(μ‐OPy)2(CO)4], OPy = 2‐pyridonate) by an iridium‐iridium bond are described. The complexes exhibit fractional averaged oxidation states of +1.5 and electronic delocalization along the metallic chain. While the axial ligands do not significantly affect the metal‐metal bond lengths, the metallic chain has a significant impact on the iridium‐L/X bond distances. The complexes show free rotation around the unsupported iridium‐iridium bond in solution, with a low‐energy transition state for the chloride chain. The absorption spectra of these complexes show characteristic bands at 438‐504 nm, which can be fine‐tuned by varying the terminal capping ligands.

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Revisit of trinickel metal string complexes [Ni₃L₄X₂] (L = dipyridylamido, diazaphenoxazine; X = NCS, CN) for quantum transport

Lin

Cheng

Liou

et al. 2019

J Chinese Chemical Soc

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Metal string complexes contain a linear metal‐atom chain in which the metal centers are coordinated by four equatorial and two axial ligands. With a variety of transition‐metal elements and ligands, the structural framework drives the flourishing of molecular design and properties. The one‐dimensional configuration makes the compounds suitable for the studies of quantum transport across molecular junctions. In this study, we report the conductance measurements and transmission spectra of three trinickel metal strings, [Ni3(dpa)4(NCS)2] (1), [Ni3(dzp)4(NCS)2] (2), and [Ni3(dpa)4(CN)2] (3) (Hdpa = dipyridylamine, Hdzp, diazaphenoxazine) in which 1 is a prototypical compound, dzp of 2 represents an equatorial ligand more rigid than dpa of 1, and ─CN is an axial ligand with a ligand‐field effect stronger than ─NCS of 1. Measurement results of molecular junctions for 1, 2, and 3 are 2.69, 3.24, and 17.4 MΩ, respectively. The highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gaps calculated by density functional theory in the gas phase for 1, 2, and 3 are about 2.65, 2.34, and 3.85 eV, respectively. Zero‐bias transmission spectra of 1–3 show that transmission peaks lie just above EFermi (the Fermi energy of the gold electrode), suggesting LUMO‐dominant transport pathways. The transmission peaks at EFermi are associated with LUMO+2 found in the gas phase. LUMOs in the free space are located at nearly 1 eV below EFermi. The shift of molecular orbitals from their isolated form and the alignment of LUMO+2 with the electrode Fermi level manifest the importance and significant of the electrodes' self‐energy on electron transport.

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Pentanuclear Heterometallic String Complexes with High‐Bond‐order Units [Ni₂³⁺−Mo₂⁴⁺−Ni²⁺(bna)₄X₂]³⁺ (X = Cl, NCS)

Cited by 9 publications

References 45 publications

Coordination Ladder Polymers: Helical Metal Strings

Coordination Ladder Polymers: Helical Metal Strings

Mixed‐Valence Tetrametallic Iridium Chains

Revisit of trinickel metal string complexes [Ni₃L₄X₂] (L = dipyridylamido, diazaphenoxazine; X = NCS, CN) for quantum transport

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Pentanuclear Heterometallic String Complexes with High‐Bond‐order Units [Ni23+−Mo24+−Ni2+(bna)4X2]3+ (X = Cl, NCS)

Cited by 9 publications

References 45 publications

Coordination Ladder Polymers: Helical Metal Strings

Coordination Ladder Polymers: Helical Metal Strings

Mixed‐Valence Tetrametallic Iridium Chains

Revisit of trinickel metal string complexes [Ni3L4X2] (L = dipyridylamido, diazaphenoxazine; X = NCS, CN) for quantum transport

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Pentanuclear Heterometallic String Complexes with High‐Bond‐order Units [Ni₂³⁺−Mo₂⁴⁺−Ni²⁺(bna)₄X₂]³⁺ (X = Cl, NCS)

Revisit of trinickel metal string complexes [Ni₃L₄X₂] (L = dipyridylamido, diazaphenoxazine; X = NCS, CN) for quantum transport