TY - JOUR
T1 - A new generation of metal string complexes
T2 - Structure, magnetism, spectroscopy, theoretical analysis, and single molecular conductance of an unusual mixed-valence linear [Ni5]8+ complex
AU - Liu, Isiah Po Chun
AU - Bénard, Marc
AU - Hasanov, Hasan
AU - Chen, I. Wen Peter
AU - Tseng, Wei Hsiang
AU - Fu, Ming Dung
AU - Rohmer, Marie Madeleine
AU - Chen, Chun Hsien
AU - Lee, Gene Hsiang
AU - Peng, Shie Ming
PY - 2007
Y1 - 2007
N2 - Two new linear pentanickel complexes [Ni,(bna)4(Cl) 2][PF6]2 (1) and [Ni5(bna) 4(Cl)2][PF6]4 (2; bna = binaphthyridylamide). were synthesized and structurally characterized. A derivative of 1, [Ni5(bna)4(NCS)2][NCS] 2 (3), was also isolated for the purpose of the conductance experiments carried out in comparison with [Ni5(tpda) 4-(NCS)2] (4; tpda = tripyridyldiamide). The metal framework of complex 2 is a standard [Ni5]10+ core, isoelectronic with that of [Ni5(tpda)4Cl2] (5). Also as in 5. complex 2 has an antiferromagnetic ground state (J = -15.86 cm-1) resulting from a coupling between the terminal nickel atoms, both in high-spin sate (5=1). Complex 1 displays the first characterized linear nickel framework in which the usual sequence of NiII atoms has been reduced by two electrons. Each dinickel unit attached to the naphthyridyl moieties is assumed to undergo a one-electron reduction, whereas the central nickel formally remains NiII. DFT; calculations suggest that the metal framework of the mixed-valence complex 1 should be described as intermediate between a localized picture corresponding to NiII- NiI-NiII-NiI-NiII and a fully delocalized model represented as (Ni2)3+-Ni II-(Ni2)3+. Assuming the latter model, the ground state of 1 results from an antiferromagnetic coupling (J = -34.03 cm -1) between the two (Ni2)3+ fragments, considered each as a single magnetic centre (5 = 3/2). An intervalence charge-transfer band is observed in the NIR spectrum of 1 at 1186nm, suggesting, in accordance with DFT calculations, that 1 should be assigned to Robin-Day class II of mixed-valent complexes. Scanning tunnelling microscopy (STM) methodology was used to assess the conductance of single molecules of 3 and 4. Compound 3 was found ≈ 40% more conductive than 4, a result that could be assigned to the electron mobility induced by mixed-valency in the naphthyridyl fragments.
AB - Two new linear pentanickel complexes [Ni,(bna)4(Cl) 2][PF6]2 (1) and [Ni5(bna) 4(Cl)2][PF6]4 (2; bna = binaphthyridylamide). were synthesized and structurally characterized. A derivative of 1, [Ni5(bna)4(NCS)2][NCS] 2 (3), was also isolated for the purpose of the conductance experiments carried out in comparison with [Ni5(tpda) 4-(NCS)2] (4; tpda = tripyridyldiamide). The metal framework of complex 2 is a standard [Ni5]10+ core, isoelectronic with that of [Ni5(tpda)4Cl2] (5). Also as in 5. complex 2 has an antiferromagnetic ground state (J = -15.86 cm-1) resulting from a coupling between the terminal nickel atoms, both in high-spin sate (5=1). Complex 1 displays the first characterized linear nickel framework in which the usual sequence of NiII atoms has been reduced by two electrons. Each dinickel unit attached to the naphthyridyl moieties is assumed to undergo a one-electron reduction, whereas the central nickel formally remains NiII. DFT; calculations suggest that the metal framework of the mixed-valence complex 1 should be described as intermediate between a localized picture corresponding to NiII- NiI-NiII-NiI-NiII and a fully delocalized model represented as (Ni2)3+-Ni II-(Ni2)3+. Assuming the latter model, the ground state of 1 results from an antiferromagnetic coupling (J = -34.03 cm -1) between the two (Ni2)3+ fragments, considered each as a single magnetic centre (5 = 3/2). An intervalence charge-transfer band is observed in the NIR spectrum of 1 at 1186nm, suggesting, in accordance with DFT calculations, that 1 should be assigned to Robin-Day class II of mixed-valent complexes. Scanning tunnelling microscopy (STM) methodology was used to assess the conductance of single molecules of 3 and 4. Compound 3 was found ≈ 40% more conductive than 4, a result that could be assigned to the electron mobility induced by mixed-valency in the naphthyridyl fragments.
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U2 - 10.1002/chem.200700750
DO - 10.1002/chem.200700750
M3 - Article
C2 - 17847146
AN - SCOPUS:35948941314
SN - 0947-6539
VL - 13
SP - 8667
EP - 8677
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 31
ER -