TY - JOUR
T1 - The controlled formation and cleavage of an intramolecular d 8-d8 Pt-Pt interaction in a dinuclear cycloplatinated molecular "pivot-hinge"
AU - Koo, Chi Kin
AU - WONG, Ka-Leung
AU - Lau, Kai Cheung
AU - WONG, Wai Yeung
AU - Lam, Michael Hon Wah
N1 - Copyright:
Copyright 2009 Elsevier B.V., All rights reserved.
PY - 2009/8/3
Y1 - 2009/8/3
N2 - The bis(diphenylphosphino)methane (dppm)-bridged dinuclear cycloplatinated complex {[Pt(L)]2(μdpprn)}2+ (Pt2· dppm; HL: 2-phenyl-6(1 H-pyrazol-3-yl)-pyridine) demonstrates interesting reversible "pivothinge"-like intramolecular motions in response to the protonation/deprotonation of L. In its protonated "closed" configuration, the two platinum(II) centers are held in position by intramolecular d8-d8 Pt-Pt interaction. In its deprotonated "open" configuration, such Pt-Pt interaction is cleaved. To further understand the mechanism behind this hingelike motion, an analogous dinuclear cycloplatinated complex, {[Pt(L)]2(μ-dchpm)} 2+ (Pt2·dchpm) with bis(dicyclohexylphosphino) methane (dchpm) as the bridging ligand, was synthesized. From its protonation/deprotonation responses, it was revealed that aromatic π-π interactions between the phenyl moieties of the μ-dppm and the deprotonated pyrazolyl rings of L was essential to the reversible cleavage of the intramolecular Pt-Pt interaction in Pt2·dppm. In the case of Pt2·dchpm, spectroscopic and spectrofluorometric titrations as well as X-ray crystallography indicated that the distance between the two platinum(II) centers shrank upon deprotonation, thus causing a redshift in its room-temperature triplet metal-metalto-ligand charge-transfer emission from 614 to 625 nm. Ab initio calculations revealed the presence of intramolecular hydrogen bonding between the deprotonated and negatively charged 1pyrazolyl-N moiety and the methylene CH and phenyl C-H of the μ-dppm. The "open" configuration of the deprotonated Pt2·dppm was estimated to be 19 kcal mol-1 more stable than its alternative "closed" configuration. On the other hand, the open configuration of the deprotonated Pt2·dchpm was 6 kcal mol-1 less stable than its alternative closed configuration.
AB - The bis(diphenylphosphino)methane (dppm)-bridged dinuclear cycloplatinated complex {[Pt(L)]2(μdpprn)}2+ (Pt2· dppm; HL: 2-phenyl-6(1 H-pyrazol-3-yl)-pyridine) demonstrates interesting reversible "pivothinge"-like intramolecular motions in response to the protonation/deprotonation of L. In its protonated "closed" configuration, the two platinum(II) centers are held in position by intramolecular d8-d8 Pt-Pt interaction. In its deprotonated "open" configuration, such Pt-Pt interaction is cleaved. To further understand the mechanism behind this hingelike motion, an analogous dinuclear cycloplatinated complex, {[Pt(L)]2(μ-dchpm)} 2+ (Pt2·dchpm) with bis(dicyclohexylphosphino) methane (dchpm) as the bridging ligand, was synthesized. From its protonation/deprotonation responses, it was revealed that aromatic π-π interactions between the phenyl moieties of the μ-dppm and the deprotonated pyrazolyl rings of L was essential to the reversible cleavage of the intramolecular Pt-Pt interaction in Pt2·dppm. In the case of Pt2·dchpm, spectroscopic and spectrofluorometric titrations as well as X-ray crystallography indicated that the distance between the two platinum(II) centers shrank upon deprotonation, thus causing a redshift in its room-temperature triplet metal-metalto-ligand charge-transfer emission from 614 to 625 nm. Ab initio calculations revealed the presence of intramolecular hydrogen bonding between the deprotonated and negatively charged 1pyrazolyl-N moiety and the methylene CH and phenyl C-H of the μ-dppm. The "open" configuration of the deprotonated Pt2·dppm was estimated to be 19 kcal mol-1 more stable than its alternative "closed" configuration. On the other hand, the open configuration of the deprotonated Pt2·dchpm was 6 kcal mol-1 less stable than its alternative closed configuration.
KW - Ab initio calculations
KW - Metal-metal interactions
KW - Molecular machines
KW - Platinum
KW - Protonation
UR - http://www.scopus.com/inward/record.url?scp=68049087914&partnerID=8YFLogxK
U2 - 10.1002/chem.200802703
DO - 10.1002/chem.200802703
M3 - Journal article
AN - SCOPUS:68049087914
SN - 0947-6539
VL - 15
SP - 7689
EP - 7697
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 31
ER -