Formation, Reactivity, and Photorelease of Metal Bound Nitrosyl in [Ru(trpy)(L)(NO)] n + (trpy = 2,2′:6′,2′′-Terpyridine, L = 2-Phenylimidazo[4,5- f ]1,10-phenanthroline) (original) (raw)
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Inorganic …, 2008
The electrophilic {Ru− NO+} in [4] 3+ quantitatively transforms to {Ru− NO2−} in the presence of OH−, the isolated radical species {Ru− NO•} in [4] 2+ undergoes facile oxidation to {Ru− NO+} in [4] 3+ with O2, and the photoreleased NO from [4] 2+ could be trapped as ...
Dalton Transactions, 2011
The present article describes ruthenium nitrosyl complexes with the {RuNO} 6 and {RuNO} 7 notations in the selective molecular frameworks of [Ru II ([9]aneS 3)(bpy)(NO +)] 3+ (4 3+), [Ru II ([9]aneS 3)(pap) (NO +)] 3+ (8 3+) and [Ru II ([9]aneS 3)(bpy)(NO ∑)] 2+ (4 2+), [Ru II ([9]aneS 3)(pap)(NO ∑)] 2+ (8 2+) ([9]aneS 3 = 1,4,7-trithiacyclononane, bpy = 2,2¢-bipyridine, pap = 2-phenylazopyridine), respectively. The nitrosyl complexes have been synthesized by following a stepwise synthetic procedure: {Ru II-Cl} → {Ru II-CH 3 CN} → {Ru II-NO 2 } → {Ru II-NO + } → {Ru II-NO ∑ }. The single-crystal X-ray structure of 4 3+ and DFT optimised structures of 4 3+ , 8 3+ and 4 2+ , 8 2+ establish the localised linear and bent geometries for {Ru-NO + } and {Ru-NO ∑ } complexes, respectively. The crystal structures and 1 H/ 13 C NMR suggest the [333] conformation of the coordinated macrocyclic ligand ([9]aneS 3) in the complexes. The difference in p-accepting strength of the co-ligands, bpy in 4 3+ and pap in 8 3+ (bpy < pap) has been reflected in the n(NO) frequencies of 1945 cm-1 (DFT: 1943 cm-1) and 1964 cm-1 (DFT: 1966 cm-1) and E • ({Ru II-NO + }/{Ru II-NO ∑ }) of 0.49 and 0.67 V versus SCE, respectively. The n(NO) frequency of the reduced {Ru-NO ∑ } state in 4 2+ or 8 2+ however decreases to 1632 cm-1 (DFT: 1637 cm-1) or 1634 cm-1 (DFT: 1632 cm-1), respectively, with the change of the linear {Ru II-NO + } geometry in 4 3+ , 8 3+ to bent {Ru II-NO ∑ } geometry in 4 2+ , 8 2+. The preferential stabilisation of the eclipsed conformation of the bent NO in 4 2+ and 8 2+ has been supported by the DFT calculations. The reduced {Ru II-NO ∑ } exhibits free-radical EPR with partial metal contribution revealing the resonance formulation of {Ru II-NO ∑ }(major)↔{Ru I-NO + }(minor). The electronic transitions of the complexes have been assigned based on the TD-DFT calculations on their DFT optimised structures. The estimated second-order rate constant (k, M-1 s-1) of the reaction of the nucleophile, OHwith the electrophilic {Ru II-NO + } for the bpy derivative (4 3+) of 1.39 ¥ 10-1 is half of that determined for the pap derivative (8 3+), 2.84 ¥ 10-1 in CH 3 CN at 298 K. The Ru-NO bond in 4 3+ or 8 3+ undergoes facile photolytic cleavage to form the corresponding solvent species {Ru II-CH 3 CN}, 2 2+ or 6 2+ with widely varying rate constant values, (k NO , s-1) of 1.12 ¥ 10-1 (t 1/2 = 6.2 s) and 7.67 ¥ 10-3 (t 1/2 = 90.3 s), respectively. The photo-released NO can bind to the reduced myoglobin to yield the Mb-NO adduct.
European Journal of Inorganic Chemistry, 2009
Ruthenium nitrosyl complexes have been isolated in the {RuNO} 6 and {RuNO} 7 configurations, employing the following reaction pathway for [Ru(trpy)(bik)(X)] n+ : X = Cl-, [1](ClO 4) Ǟ X = CH 3 CN, [2](ClO 4) 2 Ǟ X = NO 2-, [3](ClO 4) Ǟ X = NO + , [4](ClO 4) 3 Ǟ X = NO • , [4](ClO 4) 2. The single-crystal X-ray structures of [1](ClO 4)•(C 6 H 6)•H 2 O, [2](ClO 4) 2 •H 2 O, and [3](ClO 4)•H 2 O have been determined. The successive NO + /NO • (reversible) and NO • /NO-(irreversible) reduction processes of [4] 3+ appear at +0.36 and-0.40 V vs. SCE, respectively. While the ν(C=O) frequency of the bik ligand at about 1630 cm-1 is largely invariant on complexation and reduction, the ν(NO) frequency for the {RuNO} 6 state in [4] 3+ at 1950 cm-1 shifts to about 1640 cm-1 on one-electron reduction to the {RuNO} 7 form in [4] 2+ , reflecting the predominant NO + Ǟ NO • character of this electron transfer. However, a sizeable contribution from ruthenium with its high spinorbit coupling constant to the singly occupied molecular or-[a
Dalton Transactions, 2011
Chemical reactivity, photolability, and computational studies of the ruthenium nitrosyl complex with a substituted cyclam, fac- [Ru(NO)Cl 2 (k 3 N 4 ,N 8 ,N 11 (1-carboxypropyl)cyclam)]Cl·H 2 O ((1-carboxypropyl)cyclam = 3-(1,4,8,11-tetraazacyclotetradecan-1-yl)propionic acid)), (I) are described. Chloride ligands do not undergo aquation reactions (at 25 • C, pH 3). The rate of nitric oxide (NO) dissociation (k obs-NO ) upon reduction of I is 2.8 s -1 at 25 ± 1 • C (in 0.5 mol L -1 HCl), which is close to the highest value found for related complexes. The uncoordinated carboxyl of I has a pK a of~3.3, which is close to that of the carboxyl of the non coordinated (1-carboxypropyl)cyclam (pK a = 3.4). Two additional pK a values were found for I at~8.0 and~11.5. Upon electrochemical reduction or under irradiation with light (l irr = 350 or 520 nm; pH 7.4), I releases NO in aqueous solution. The cyclam ring N bound to the carboxypropyl group is not coordinated, resulting in a fac configuration that affects the properties and chemical reactivities of I, especially as NO donor, compared with analogous trans complexes. Among the computational models tested, the B3LYP/ECP28MDF, cc-pVDZ resulted in smaller errors for the geometry of I. The computational data helped clarify the experimental acid-base equilibria and indicated the most favourable site for the second deprotonation, which follows that of the carboxyl group. Furthermore, it showed that by changing the pH it is possible to modulate the electron density of I with deprotonation. The calculated NO bond length and the Ru/NO charge ratio indicated that the predominant canonical structure is [Ru III NO], but the Ru-NO bond angles and bond index (b.i.) values were less clear; the angles suggested that [Ru II NO + ] could contribute to the electronic structure of I and b.i. values indicated a contribution from [Ru IV NO -]. Considering that some experimental data are consistent with a [Ru II NO + ] description, while others are in agreement with [Ru III NO], the best description for I would be a linear combination of the three canonical forms, with a higher weight for [Ru II NO + ] and [Ru III NO].
Inorganic Chemistry, 2002
The new complex trans-[NCRu(py) 4 (CN)Ru(py) 4 NO](PF 6) 3 (I) was synthesized. In acetonitrile solution, I shows an intense visible band (555 nm,) 5800 M-1 cm-1) and other absorptions below 350 nm, associated with d π f π* py and π py f π* py transitions. The visible band is presently assigned as a donor−acceptor charge transfer (DACT) transition from the remote Ru(II) to the delocalized {Ru II −NO + } moiety. Photoinduced release of NO is observed upon irradiation at the DACT band. Application of the Hush model reveals strong electronic coupling, with H DA) ∼2000 cm-1. The difference between the optical absorption energy and redox potentials for the donor and acceptor sites (Ru III,II , 1.40 V, and NO + /NO, 0.50 V, vs Ag/AgCl, 3 M KCl, respectively) (hν − ∆E red) is 1.33 eV, a large value which probably relates to the significant changes in distances and angles for the Ru−N−O moiety upon reduction. UV−vis absorptions, IR frequencies, and redox potentials are solvent-dependent. Controlled potential reduction (of NO +) and oxidation (of Ru(II) associated with the dicyano-chromophore) of I afford stable species, [NCRu II (py) 4 (CN)Ru(py) 4 NO] 2+ (I red) and [NCRu III (py) 4 (CN)Ru(py) 4 NO] 4+ (I ox), respectively, which are characterized by UV−vis and IR spectroscopies. I red shows an EPR spectrum characteristic of {Ru(II)−NO • } complexes. Compound I is electrophilically reactive in aqueous solution above pH 5: values of the equilibrium constant for the reaction [NCRu(py) 4 (CN)Ru(py) 4 NO] 3+ + 2 OHa [NCRu(py) 4 (CN)Ru(py) 4 NO 2 ] + + H 2 O, K) 3.2 ± 1.4 × 10 15 M-2 , and of the rate constant for the nucleophilic addition of OH-, k) 9.2 ± 0.2 × 10 3 M-1 s-1 (25°C, I) 1 M), are obtained, with ∆H ‡) 90.7 ± 3.8 kJ mol-1 and ∆S ‡) 135 ± 13 J K-1 mol-1. The oxidized complex, I ox , shows an enhanced electrophilic reactivity toward OH-. This addition reaction is followed by irreversible processes, which most probably lead to disproportionation of bound nitrite and other products.
Inorganic Chemistry, 2006
The new compound [Ru(bpy)(tpm)NO](ClO 4) 3 [tpm) tris(1-pyrazolyl)methane; bpy) 2,2′-bipyridine] has been prepared in a stepwise procedure that involves the conversion of [Ru(bpy)(tpm)Cl] + into the aqua and nitro intermediates, followed by acidification. The diamagnetic complex crystallizes to exhibit distorted octahedral geometry around the metal, with the Ru−N(O) bond length 1.774(12) Å and the RuNO angle 179.1(12)°, typical for a {RuNO} 6 description. The [Ru(bpy)(tpm)NO] 3+ ion (I) has been characterized by 1 H NMR and IR spectroscopies (ν NO) 1959 cm-1) and through density functional theory calculations. Intense electronic transitions in the 300−350-nm region are assigned through time-dependent (TD)DFT as intraligand π f π* for bpy and tpm. The dπ f π*(bpy) metal-to-ligand chargetransfer transitions appear at higher energies. Aqueous cyclic voltammetric studies show a reversible wave at 0.31 V (vs Ag/AgCl, 3 M Cl-), which shifts to 0.60 V in MeCN, along with the onset of a wave of an irreversible process at −0.2 V. The waves are assigned to the one-and two-electron reductions centered at the NO ligand, leading to species with {RuNO} 7 and {RuNO} 8 configurations, respectively. Controlled potential reduction of I in MeCN led to the [Ru(bpy)(tpm)NO] 2+ ion (II), revealing a significant downward shift of ν NO to 1660 cm-1 as well as changes in the electronic absorption bands. II was also characterized by electron paramagnetic resonance, showing an anisotropic signal at 110 K that arises from an S) 1 / 2 electronic ground state; the g-matrix components and hyperfine coupling tensor resemble the behavior of related {RuNO} 7 complexes. Both I and II were characterized through their main reactivity modes, electrophilic and nucleophilic, respectively. The addition of OHinto I generated the nitro complex, with k OH) 3.05 × 10 6 M-1 s-1 (25°C). This value is among the highest obtained for related nitrosyl complexes and correlates with E NO + /NO , the one-electron redox potential. Complex II is a robust species toward NO release, although a conversion to I was observed in the presence of O 2. This reaction afforded a second-order rate law with k) 3.5 M-1 s-1 (25°C). The stabilization of the NO radical complex is attributed to the high positive charge of the precursor and to the geometrical and electronic structure as determined by the neutral tpm ligand.
Inorganica Chimica …, 2006
The photochemical and pharmacological studies of the novel [Ru(L)(tpy)NO]3+ L = bpy (2,2′-bipyridine), NH · NHq (quinonediimine) and NH2.NH2cat (o-phenylenediamine) were investigated in aqueous medium. The synthesized nitrosyl ruthenium complexes showed nitric oxide (NO) release under light irradiation at 355 nm for [Ru(L)(tpy)NO]3+ complex with quantum yield of 0.14 ± 0.02, 0.47 ± 0.03 and 0.46 ± 0.02 mol Einstein−1 for L = bpy, NH · NHq and NH2 · NH2cat, respectively, and 0.0065 ± 0.001 mol Einstein−1 for light irradiation at 532 nm for [Ru(NH · NHq)(tpy)NO]3+ complex. The photochemical pathway at 355 nm light irradiation was described as a multi-step mechanism, although at 532 nm it was better attributed to a photo-induced electron transfer. The vasorelaxation induced by NO release produced by light irradiation in visible region from physiological solution of [Ru(NH · NHq)(tpy)NO]3+ complex was evaluated and compared with sodium nitroprusside (SNP). The results showed very similar vasodilator power between both species.The photochemical and pharmacological studies of the novel [Ru(L)(tpy)NO]3+ L = bpy (2,2′-bipyridine), NH · NHq (quinonediimine) and NH2 · NH2cat (o-phenylenediamine) were investigated in aqueous medium. The synthesized nitrosyl ruthenium complexes showed nitric oxide (NO) release under light irradiation at 355 nm for [Ru(L)(tpy)NO]3+ and 532 nm for [Ru(NH · NHq)(tpy)NO]3+. Both systems show vasodilation properties due to the NO release.
Inorganic Chemistry, 1990
The reactions of the anionic cluster [Ru,(CO),,(NO)]-with acids and CF3S03CH3 are reported. 0-Methylation of the p2-N0 ligand gives high yields of Ru,(NOCH,)(CO),,. A single-crystal X-ra crystallographic analysis of this new cluster [orthorhombic crystal system, Pnma space group, a = 14.775 (4) A, b = 12.128 (2) AI , c = 9.987 (2) A, Z = 41 revealed the presence of a triply bridging methoxyimido (NOCHJ ligand and a triply bridging carbonyl ligand on opposite faces of an equilateral ruthenium triangle. 0-Protonation with CF3S03H gives an analogous structure; however, weaker acids, such as CF3C02H, give only HRU,(CO),~(NO), where a Ru-Ru bond has been protonated. Addition of PPN(CF,CO,) to RU,(NOH)(CO),~ results in immediate 0-H to M-H tautomerization. The PPN+ salts of 12 anions having differing basicities provide insight into the pK, of R U~(N O H) (C O)~~ and the relative kinetic acidity of the 0-H vs the M-H group. Reactions of the substituted anions [Ru3(CO),(L)(NO)]-, where L = PPhp and P(OCH3),, with acids reveal similar behavior.
Photochemical NO release from nitrosyl Ru(II) complexes with C-bound imidazoles
a b s t r a c t The series of nitrosyl complexes trans-[Ru(NH 3 ) 4 L(NO)]Cl 3 , L = caffeine, theophylline, imidazole and benzoimidazole in position trans to NO were prepared and their photochemical properties studied. All complexes showed nitric oxide (NO) release under light irradiation at 330-440 nm. Quantum yields for [Ru(NH 3 ) 4 L(H 2 O)] 3+ formation (/ Ru(III) ) were sensitive to the natures of L, k irr and pH. The major product of the irradiation of trans-[Ru(NH 3 ) 4 L(NO + )] 3+ is the trans-[Ru III (NH 3 ) 4 L(Cl)] 2+ and NO as suggested by UV-Vis, electrochemical, and FTIR techniques.