A novel fluorescent nanoprobe that based on poly(thymine) single strand DNA-templated copper nanocluster for the detection of hydrogen peroxide.

In this paper, a label-free fluorescence nanoprobe is constructed based on poly(thymine) single strand DNA-templated Copper nanocluster (denote as: T-CuNCs) for the detection of hydrogen peroxide. In the assay, the fluorescent T-CuNCs will generate though the reaction of Cu2+, poly(thymine) and sodium ascorbate. However, the hydroxyl radical (.OH) will generated in the presence of H2O2, which is able to induced the oxidative lesions of poly(thymine) single chain DNA and lead to the poly(thymine) being splitted into shorter or single oligonucleotide fragments and lose the ability to template the fluorescent T-CuNCs again. Therefore, H2O2 can be detected by monitoring the fluorescence strength change of T-CuNCs. The experimental results show that the fluorescence intensity change of T-CuNCs has fantastic linearity versus H2O2 concentration in the range of 1-30 µM (R2 = 0.9947) and 30-80 µM (R2 = 0.9972) with the limit of detection (LOD) as low as 0.5 µM (S/N = 3). More important, the fluorescent nanoprobe was also successfully utilized on the detection of H2O2 in serum samples. Therefore, a label-free, costless and effective fluorescence method has been established for the detection of H2O2, the intrinsic properties of the nanoprobe endow its more potential applications in chemical and biological study.

From zero-dimensional to one-dimensional chain N-oxide bridged compounds with enhanced single-molecule magnetic performance.

A series of dinuclear dysprosium complexes bridged by pyridine-NO ligands with formula [Ln2(BTA)6(pyNO)2] (1Dy, Ln = Dy, 1Y, Ln = Y and 1Gd, Ln = Gd) (BTA = benzoyltrifluoroacetone, pyNO = pyridine-N-oxide) were structurally and magnetically characterized. The X-ray crystallographic analyses of the structures revealed that the NO group serves as the effective bridge to link two Dy(iii) centers and the periphery ß-diketonate (BTA) ligands complete the rest of the coordination sphere. The dynamic magnetic measurements revealed that complex 1Dy displayed significant zero-field single-molecule magnetic (SMM) behaviour with 72 K energy barrier and 2.5 K hysteresis temperature. In order to extend this dinuclear system, double N-oxide bridged ligand 4,4'-bpdo(4,4'-bipyridine-N,N'-dioxide) was used, and consequently, a series of one-dimensional chain complexes possessing repeated [Ln2(BTA)6(pyNO)2] units were synthesized with formula [Ln2(BTA)6(4,4'-bpdo)]n·2EtOH (2Dy, Ln = Dy, 2Y, Ln = Y and 2Gd, Ln = Gd). The AC magnetic susceptibility measurements revealed that complex 2Dy exhibited significant zero-field slow magnetic relaxation behavior with a higher effective energy barrier of 87 K and a hysteresis temperature of 3 K than 1Dy albeit the separation between the repeated units is large.

High local coordination symmetry around the spin center and the alignment between magnetic and symmetric axes together play a crucial role in single-molecule magnet performance.

A tetradentate 8-hydroxyquinoline-based acyl hydrazone ligand (HL1 = 8-hydroxyquinoline-2-carboxaldehyde-(aminourea)hydrochloride) was elaborately used to construct a mononuclear dysprosium complex DyCl3HL1·CH3OH (1) with a nearly ideal pentagonal bipyramid coordination geometry (D5h) surrounding the Dy(iii) ion to achieve the significant performance of single-molecule magnets (SMMs). Meanwhile, the isolated high local symmetry center was successfully kept intact and further bridged to a series of double bipyramid systems by two phenolic oxygen atoms of the acyl hydrazone ligands (HL1 and HL2 = 8-hydroxyquinoline-2-carboxaldehyde-(benzoyl)hydrazine), with the formulae [Dy2Cl4(L1)2(CH3OH)2]·4C5H5N (2) and [Dy2Cl4(L2)2]·2CH3CN (3). In addition, the monodentate co-ligand anion was replaced by a larger sterically hindered ligand and a bidentate monovalent ß-diketonate anion to generate [Dy2(tfo)4(L2)2(EtOH)2] (4), [Dy2(tta)4(L2)2(EtOH)2]·2(EtOH) (5) and [Dy2(dbm)4(L2)2(EtOH)2] (6) (tfo = trifluoromethanesulfonic acid, dbm = dibenzoylmethane, tta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione) with eight-coordinate geometry. Strikingly, the dynamic magnetic measurements revealed that complexes 1-3 did not display the expected significant SMM performance albeit they had high local symmetry. In combination with ab initio calculation, the alignment of the coordination symmetric axis and the magnetic easy axis dominates the molecular magnetic anisotropy, and the magnetic easy axis could be modulated by the distribution of coordination atoms with different electrostatic properties.

Modulation of the Coordination Environment around the Magnetic Easy Axis Leads to Significant Magnetic Relaxations in a Series of 3d-4f Schiff Complexes.

A series of Salen-type Zn(II)-Dy(III) complexes [L1Zn(II)ClDy(III)(acac)2]·H2O (1), [L1Zn(II)BrDy(III)(acac)2]·H2O (2), [L1Zn(II)(H2O)Dy(III)(acac)2]·CH2Cl2·PF6 (3), [L2Zn(II)(H2O)Dy(III)(acac)2]·PF6 (4), and Co(III)-Dy(III) complexes [L1Co(III)Br2Dy(III)(acac)2]·CH2Cl2 (5), [L2Co(III)Cl2Dy(III)(acac)Cl(MeO)] (6), [L2Co(III)Cl2Dy(III)(acac)Cl(H2O)] (7), and [L2Co(III)Cl2Dy(III)(NO3)2(MeO)] (8) heterobinuclear single-molecule magnets (SMMs) were synthesized and magnetically characterized. These complexes were constructed by incorporating diamagnetic Zn(II) and Co(III) ions with acetylacetone (acac) and compartmental Schiff-base ligands (H2L1 = N, N'-bis(2-oxy-3-methoxybenzylidene)-1,2-phenylenediamine; H2L2 = N, N'-bis(2-oxy-3-methoxybenzylidene)-1,2-diaminocyclohexane). In the Zn(II)-Dy(III) (1-4) system, the coordination environments of the Dy(III) ions are nearly identical, but the apical coordination atom to the Zn(II) ion is different. Complexes 1, 2, and 4 displayed no magnetic relaxation in the absence of external magnetic field, but complex 3 displayed more pronounced SMM behavior with a relaxation energy barrier Ueff/ kB 38 K and magnetic hysteresis at 1.8 K. The SMM performances of 5, 6, and 7 were enhanced significantly by incorporating an octahedral Co(III) instead of square-pyramidal Zn(II) and replacing one of acac- group around Dy(III) ion by a neutral O atom, displaying Ueff of 167, 118, and 75 K as well as magnetic hysteresis up to 3.5 K. These studies indicated that the remote diamagnetic Zn(II) and Co(III) ions played a key role, and the SMM properties were very strongly related to the special coordination atoms configuration around Dy(III) ion. When this coordination configuration around was broken as 8 exhibited, however, it resulted in a dramatically decreased SMM performance. From this work, the key factors that significantly affect the SMM performance of these heteronuclear Zn(II)/Co(III)-Dy(III) SMMs are unambiguously presented.

Strictly linear trinuclear Dy-Ca/Mg-Dy single-molecule magnets: the impact of long-range f-f ferromagnetic interactions on suppressing quantum tunnelling of magnetization leading to slow magnetic relaxation.

The synthesis, structural characterization and magnetic properties of four heterometallic complexes with formulas Ln2M(OQ)8 [Ln(iii) = Dy, M(ii) = Ca (1), Mg (2); Ln(iii) = Er, M(ii) = Ca (3), Mg (4); HOQ = 8-hydroxyquinoline] are reported. Complexes display a perfectly linear arrangement of three metal ions involving two terminal Ln(iii) ions and one central alkaline earth M(ii) ion, and they are bridged by three phenolato oxygen atoms from three 8-hydroxyquinoline ligands. Direct-current (dc) magnetic susceptibility studies show that there exists a long-range ferromagnetic (FM) interaction between two f-electronic centers in Dy-based complexes 1 and 2 albeit they are separated by diamagnetic alkaline earth ions, and the FM interaction has been successfully reproduced by ab initio calculations. Alternating current (ac) magnetic susceptibility measurements indicate that complexes 1 and 2 exhibit significant single-molecule magnet (SMM) behaviors. This is mostly attributed to the parallel magnetic axes of individual Dy(iii) sites aligning closely to the Dy-M-Dy direction, and the linearly extending magnetic susceptibility tensors of each ion lead to the FM interaction. The dc and ac susceptibility studies of the intramolecularly diluted complexes reveal that the f-f coupling suppresses the QTMs significantly in the absence of the external magnetic field.

A series of dinuclear Dy(iii) complexes bridged by 2-methyl-8-hydroxylquinoline: replacement on the periphery coordinated ß-diketonate terminal leads to different single-molecule magnetic properties.

A series of HMq-bridged dinuclear dysprosium complexes, namely, [Dy(acac)2(CH3OH)]2(µ-HMq)2 (1), [Dy(DBM)2]2(µ-HMq)2(n-C6H14) (2), [Dy(hmac)2]2(µ-HMq)2 (3) and [Dy(hfac)3]2(µ-HMq)2 (4) (HMq = 2-methyl-8-hydroxyquinoline, acac = acetylacetone, DBM = dibenzoylmethane, hmac = hexamethylacetylacetonate and hfac = hexafluoroacetylacetonate), were structurally and magnetically characterized. X-ray crystallographic analyses of the structures reveal that HMq serves as the effective bridge to link two Dy(III) centers by means of the phenoxyl oxygen and nitrogen atoms and the periphery ß-diketonate ligands complete the coordination sphere by bidentate oxygen atoms. The different substituents on the ß-diketonate terminal lead to different coordination models mostly due to the steric hindrance of these substituents, and the electron-withdrawing or donating effects likely influence the strength of the ligand fields and the Dy(III) ion anisotropy. Measurements of alternating-current (ac) susceptibility on complexes 1-4 reveal that complexes 3 and 4 display significant zero-field single-molecule magnetic (SMM) behavior with barrier energy Ueff/kB = 14.8 K, τ0 = 1.8 × 10(-5) s and Ueff/kB = 9.2 K, τ0 = 1.7 × 10(-5) s, respectively, whereas 1 and 2 exhibit field-induced SMM behavior, and these differences are attributed to the alteration on the periphery ß-diketonate ligands. Their distinct slow magnetic relaxation behaviors were related to their different individual Dy(III) ion magnetic anisotropy and intramolecular coupling, which were confirmed by ab initio calculations.

A family of tetranuclear quinolinolate Dy(iii)-based single-molecule magnets: effects of periphery ligand replacement on their magnetic relaxation.

Three complexes with formula {Dy(q)2(L)}2(µ3-OH)2{Dy(q)(L)}2(solvents) (where q = 8-quinolinolate; L = acetylacetone (acac) with (CH2Cl2)2 = solvent (1), 1,3-diphenyl-1,3-propanedione (DBM) and (CH2Cl2)2 = solvent (2), and hexafluoroacetylacetone (hfac) and CHCl3 = solvent (3)) were structurally and magnetically characterized. They have similar Dy4 structural cores bridged by N and O atoms from 8-quinolinolate, and only differ in the peripheral ß-diketonate ligands. The variable-frequency and temperature alternating-current (ac) magnetic susceptibility measurements reveal that complexes 1 and 2 display significant zero-field single-molecule-magnet (SMM) behavior, while complex 3 exhibits the field-induced SMM behavior, albeit they possess the nearly same primary coordination sphere. The ac susceptibility measurement on the diluted samples verified that their relaxation was of purely molecular origin, and their distinct slow magnetic behaviors were related to the replacement of the peripheral ß-diketonate ligand, which is responsible for their different individual Dy(iii) ions' magnetic anisotropy and intramolecular coupling, as confirmed by ab initio calculation.

Series of dinuclear and tetranuclear lanthanide clusters encapsulated by salen-type and ß-diketionate ligands: single-molecule magnet and fluorescence properties.

Three dinuclear [Ln2H2OL(1)2(acac)2]·solvent (1, Ln = Gd, solvent = 2CH2Cl2; 2, Ln = Tb, no solvent; 3, Ln = Er, solvent = (C2H5)2O), and two tetranuclear lanthanide clusters [Ln4(µ3-OH)2L(2)2(acac)6]·2(solvent) (4, Ln = Tb, solvent = CH3OH; 5, Ln = Dy, solvent = CH3CN) were characterized in terms of structure, fluorescence and magnetism. The dinuclear lanthanide complexes were constructed by a rigid salen-type ligand H2L(1) = N,N'-bis(salicylidene)-o-phenylenediamine and ß-diketonate (acac = acetylacetonate) ligands, while the tetranuclear clusters were formed from the flexible ligand H2L(2) = N,N'-bis(salicylidene)-1,2-ethanediamine. Crystal structure analysis indicates that the rigid ligand favors the double-decker sandwich structure (Ln2L(1)2), in which the two lanthanide ions have different coordination numbers and geometry, while the more flexible ligand (H2L(2)) leads to planar tetranuclear clusters. The relationship between their respective magnetic anisotropy and ligand-field geometries and their fluorescence properties was investigated. The Dy and Tb-containing clusters exhibit typical visible fluorescence properties, and single-molecule magnet behavior is seen in complex 5.

Ytterbium can relax slowly too: a field-induced Yb2 single-molecule magnet.

An unusual dinuclear Yb(2) complex isolated using a mixed ligand strategy leads to field-induced SMM behaviour. Low magnetic axiality and a large tunnelling gap lead to significant quantum tunnelling of the magnetisation, which was reduced under an applied static optimum field of 1600 Oe.

A salen-type trinuclear Zn2Gd complex.

In the trinuclear title complex, di-µ-acetato-1:2κ(2)O:O';2:3κ(2)O:O'-bis-{µ-6,6'-dimeth-oxy-2,2'-[cyclo-hexane-1,2-diylbis(methanylyl-idene)]diphenolato}-1:2κ(6)O(1),N,N',O(1'):O(6),O(6');2:3κ(6)O(6),O(6'):O(1),N,N',O(1')-2-gadolinium(III)-1,3-dizinc hexa-fluor-idophosphate methanol monosolvate monohydrate, [GdZn2(C22H24N2O4)2(CH3COO)2]PF6·CH3OH·H2O, the two Zn(II) ions are located in the inner N2O2 cavities of two 6,6'-dimeth-oxy-2,2'-[cyclo-hexane-1,2-diylbis(methanylyl-idene)]diphenolate (L) ligands. Both Zn(II) ions are five-coordinated by two O atoms and two N atoms from the L ligand and one O atom of an acetic acid mol-ecule, giving rise to a square-pyramidal geometry around the Zn(II) ions. The Gd(III) ion is nine-coordinated by four O atoms from the outer O2O2 sites of one ligand, and three O atoms from another ligand, in which there is one non-coordinating meth-oxy O atom. Two further O atom from different acetate ligands complete the nine-coordinate environment.

Study of normal Chinese vertebral-basilar arteries with transcranial color Doppler flow imaging.

OBJECTIVE: The aim of this study was to evaluate the blood flow characteristics of intracranial vertebral-basilar artery (V-BA) in healthy Chinese adults with transcranial color Doppler flow imaging (TCDFI) and provide reference values of healthy people of different ages and genders. METHODS: Three hundred healthy Chinese adults were divided into three groups based on their ages: Group I: 20-39 years, Group II: 40-59 years, Group III: >/=60 years. Each group was subdivided into two subgroups according to their gender. Peak systolic velocity (Ps), end-diastolic velocity (Vd), time average maximum velocity (TAMAX), pulsatility index (PI), and resistance index (RI) were measured from intracranial V-BA scanning. RESULTS: Ps, Vd, and TAMAX decreased with age, while PI and RI increased in all groups. Flow velocity in women was slightly higher than that of men, and there was significant differences in group III between men and women (P<.05). However, no difference was found in the flow parameters between left and right vertebral arteries. CONCLUSIONS: This study offered reference values of intracranial V-BA flow parameters in healthy Chinese adults and indicated that these parameters varied with age and gender.