“…28 [Pt(nta)Cl] -, which is closely related structurally to the metallo headgroups of [Pt 2 (hdta)Cl 2 ] 2-, has an AB pattern centered at 4.32 ppm with J ab ) 16.34 Hz. 27 The chemical shift pattern of the tether chain follows the same trend as [Pd 2 (egta)Cl 2 ] 2-. 25,26 The CH 2 nearest the coordinating N shifts upfield upon coordination.…”
Section: Resultsmentioning
confidence: 65%
“…For comparison, [Pt(edda)] has a J ab of 16.7 Hz . [Pt(nta)Cl] - , which is closely related structurally to the metallo headgroups of [Pt 2 (hdta)Cl 2 ] 2- , has an AB pattern centered at 4.32 ppm with J ab = 16.34 Hz 1
1 T = 25.0 °CΔδ a δ (ppm) T = 75.0 °C δ (ppm) complex H 1 (a) 4.31 (d)} c −0.25 4.30 (d) 4.77 (d)} d H 1 (b) 3.89 (d)} 3.89 (d) 4.39 (d)} H 2 2.91 (t) +0.35 2.90 (t) 3.41 (t) H 3 2.14 (br s) −0.34 2.15 (br s) 2.61 (br s) H 4 1.65 (br s) −0.75 1.65 (br s) 2.17 (br s) free ligand b H 1 3.85 H 2 3.26 H 3 1.80 H 4 1.40 a A positive shift (Δδ) is an upfield shift.
…”
Section: Resultsmentioning
confidence: 99%
“…The sample was stirred magnetically in a water bath to control the temperature. The pH was adjusted initially to 1.6 with 1.0 M HCl, and the sample was stirred at room temperature for 15 h. It is known from prior studies of platinum(II) aminocarboxylates that, to prevent precipitation of Pt metal or its hydroxides, the first addition of amine donors must be carried out in acidic conditions near a pH of 2. − The further chelation of carboxylate donors is then carried out by stepwise increases in pH to values near pH 4, and then pH 6. This procedure was adopted in the present work.…”
Light yellow crystals of [MV][Pt(2)(hdta)Cl(2)].4H(2)O (1) (MV(2+) = 1,1'-dimethyl-4,4'-bipyridinium, hdta(4)(-) = 1,6-hexanediamine-N,N,N',N'-tetraacetate) were examined by X-ray diffraction. A 0.08 x 0.24 x 0.24 nm crystal was shown to have space group C2/c, having unit cell dimensions of a = 22.757(5) Å, b = 13.566(3) Å, and c = 12.120(2) Å and unit cell angles of alpha = gamma = 90 degrees and beta = 109.07(3) degrees with Z = 4. A total of 3195 independent reflections were refined to R = 0.0454. Each Pt(II) site has the anticipated NO(2)Cl square-planar mer coordination. The Pt-N(1) distance (N(1) is the N donor of the hdta(4)(-) ligand) is 2.001(9) Å, only slightly shorter than typical Pt-N distances (2.04-2.09 Å) for sp(3) donors. The Pt-O distances to the coordinated glycinato donors in 1 are 2.012(7) and 2.000(8) Å, values very similar to those of trans-[Pt(gly)(2)] (gly = glycinate). The Pt-Cl distance of 2.310(3) Å is in the range of 2.27-2.32 Å observed for other Pt(II)-Cl(-) bonds. The bond angles are close to the ideal 90 degrees or 180 degrees value: angleN-Pt-O = 85.4(3) degrees and 83.2(4) degrees; angleN-Pt-Cl = 176.6(2) degrees. The [Pt(2)(hdta)Cl(2)](2)(-) units are packed in an end-to-end fashion such that the [Pt(II)(iminodiacetate)Cl] headgroups are overlapping. This provides square-planar to square-planar stacking of the headgroups. (1)H and (13)C NMR data are presented which show that the [Pt(2)(hdta)Cl(2)](2)(-) coordination of the solid state is maintained in solution. The coordinated glycinato arms of [Pt(2)(hdta)Cl(2)](2)(-) are equivalent, exhibiting only one AB pattern in the (1)H NMR (H(a), 4.31 ppm; H(b), 3.89 ppm; J(ab) = 16.1 Hz) and one type of coordinated carboxylate ((13)C NMR resonance at 189.7 ppm). Time-dependent (1)H and (13)C NMR spectra show that inosine first displaces only Cl(-) in [Pt(2)(hdta)Cl(2)](2)(-) in solutions up to one inosine per Pt(II) center. A higher concentration of inosines (Ino) results in the displacement of one of the glycinato arms, detectable at 175.0 ppm by (13)C NMR. The sequential nature and binding of two Ino ligands, necessarily cis in [Pt(2)(hdta)(Ino)(4)], mimics the steps necessary to allow major groove-spanning ligation of DNA in the manner of the Farrell-type binuclear platinum(II) amine complexes.
“…28 [Pt(nta)Cl] -, which is closely related structurally to the metallo headgroups of [Pt 2 (hdta)Cl 2 ] 2-, has an AB pattern centered at 4.32 ppm with J ab ) 16.34 Hz. 27 The chemical shift pattern of the tether chain follows the same trend as [Pd 2 (egta)Cl 2 ] 2-. 25,26 The CH 2 nearest the coordinating N shifts upfield upon coordination.…”
Section: Resultsmentioning
confidence: 65%
“…For comparison, [Pt(edda)] has a J ab of 16.7 Hz . [Pt(nta)Cl] - , which is closely related structurally to the metallo headgroups of [Pt 2 (hdta)Cl 2 ] 2- , has an AB pattern centered at 4.32 ppm with J ab = 16.34 Hz 1
1 T = 25.0 °CΔδ a δ (ppm) T = 75.0 °C δ (ppm) complex H 1 (a) 4.31 (d)} c −0.25 4.30 (d) 4.77 (d)} d H 1 (b) 3.89 (d)} 3.89 (d) 4.39 (d)} H 2 2.91 (t) +0.35 2.90 (t) 3.41 (t) H 3 2.14 (br s) −0.34 2.15 (br s) 2.61 (br s) H 4 1.65 (br s) −0.75 1.65 (br s) 2.17 (br s) free ligand b H 1 3.85 H 2 3.26 H 3 1.80 H 4 1.40 a A positive shift (Δδ) is an upfield shift.
…”
Section: Resultsmentioning
confidence: 99%
“…The sample was stirred magnetically in a water bath to control the temperature. The pH was adjusted initially to 1.6 with 1.0 M HCl, and the sample was stirred at room temperature for 15 h. It is known from prior studies of platinum(II) aminocarboxylates that, to prevent precipitation of Pt metal or its hydroxides, the first addition of amine donors must be carried out in acidic conditions near a pH of 2. − The further chelation of carboxylate donors is then carried out by stepwise increases in pH to values near pH 4, and then pH 6. This procedure was adopted in the present work.…”
Light yellow crystals of [MV][Pt(2)(hdta)Cl(2)].4H(2)O (1) (MV(2+) = 1,1'-dimethyl-4,4'-bipyridinium, hdta(4)(-) = 1,6-hexanediamine-N,N,N',N'-tetraacetate) were examined by X-ray diffraction. A 0.08 x 0.24 x 0.24 nm crystal was shown to have space group C2/c, having unit cell dimensions of a = 22.757(5) Å, b = 13.566(3) Å, and c = 12.120(2) Å and unit cell angles of alpha = gamma = 90 degrees and beta = 109.07(3) degrees with Z = 4. A total of 3195 independent reflections were refined to R = 0.0454. Each Pt(II) site has the anticipated NO(2)Cl square-planar mer coordination. The Pt-N(1) distance (N(1) is the N donor of the hdta(4)(-) ligand) is 2.001(9) Å, only slightly shorter than typical Pt-N distances (2.04-2.09 Å) for sp(3) donors. The Pt-O distances to the coordinated glycinato donors in 1 are 2.012(7) and 2.000(8) Å, values very similar to those of trans-[Pt(gly)(2)] (gly = glycinate). The Pt-Cl distance of 2.310(3) Å is in the range of 2.27-2.32 Å observed for other Pt(II)-Cl(-) bonds. The bond angles are close to the ideal 90 degrees or 180 degrees value: angleN-Pt-O = 85.4(3) degrees and 83.2(4) degrees; angleN-Pt-Cl = 176.6(2) degrees. The [Pt(2)(hdta)Cl(2)](2)(-) units are packed in an end-to-end fashion such that the [Pt(II)(iminodiacetate)Cl] headgroups are overlapping. This provides square-planar to square-planar stacking of the headgroups. (1)H and (13)C NMR data are presented which show that the [Pt(2)(hdta)Cl(2)](2)(-) coordination of the solid state is maintained in solution. The coordinated glycinato arms of [Pt(2)(hdta)Cl(2)](2)(-) are equivalent, exhibiting only one AB pattern in the (1)H NMR (H(a), 4.31 ppm; H(b), 3.89 ppm; J(ab) = 16.1 Hz) and one type of coordinated carboxylate ((13)C NMR resonance at 189.7 ppm). Time-dependent (1)H and (13)C NMR spectra show that inosine first displaces only Cl(-) in [Pt(2)(hdta)Cl(2)](2)(-) in solutions up to one inosine per Pt(II) center. A higher concentration of inosines (Ino) results in the displacement of one of the glycinato arms, detectable at 175.0 ppm by (13)C NMR. The sequential nature and binding of two Ino ligands, necessarily cis in [Pt(2)(hdta)(Ino)(4)], mimics the steps necessary to allow major groove-spanning ligation of DNA in the manner of the Farrell-type binuclear platinum(II) amine complexes.
“…The 300 MHz NMR spectra were obtained on Bruker 300AF spectrometers for samples in D 2 O referenced to DSS (0.00 ppm) at 25 °C by following prior procedures for other Pt II , Pd II , and Ru II aminocarboxylate complexes. − …”
Section: Methodsmentioning
confidence: 99%
“…32 The 300 MHz NMR spectra were obtained on Bruker 300AF spectrometers for samples in D2O referenced to DSS (0.00 ppm) at 25 °C by following prior procedures for other Pt II , Pd II , and Ru II aminocarboxylate complexes. [22][23][24][25][26][27] EPR spectra were obtained at 120 K on a JEOL RE1X EPR instrument with a flowing-nitrogen-cooled cavity. The methods were those of previous publications from this laboratory.…”
The coordination of peptides Ser-Pro-His-His-Gly-Gly (SPHHGG) and (His)6 (HHHHHH) to [PdII(mida)(D2O)] (mida2- = N-methyliminodiacetate) was studied by 1H NMR as model reactions for CuII(iminodiacetate)-immobilized metal affinity chromatography (IMAC) sites. This is the first direct physical description of peptide coordination for IMAC. A three-site coordination is observed which involves the first, third, and fourth residues along the peptide chain. The presence of proline in position 2 of SPHHGG achieves the best molecular mechanics and bonding angles in the coordinated peptide and enhances the interaction of the serine amino nitrogen. Histidine coordination of H1, H3, and H4 of (His)6 and H3 and H4 of SPHHGG was detected by 1H NMR contact shifts and H/D exchange of histidyl protons. The EPR spectra of SPHHGG and HHHHHH attached to the [CuII(mida)] unit were obtained for additional modeling of IMAC sites. EPR parameters of the parent [Cu(mida)(H2O)2] complex are representative: gzz = 2.31; gyy = 2.086; gxx = 2.053; A parallel = 161G; AN = 19G (three line, one N coupling). Increased rhombic distortion is detected relative to the starting aqua complex in the order of [Cu(mida)L] for distortion of HHHHHH > SPHHGG > (H2O)2. The lowering of symmetry is also seen in the decrease in the N-shf coupling, presumably to the imino nitrogen of mida2- in the order 19 G (H2O), 16 G (SPHHGG) and 11 G (HHHHHH). Visible spectra of the [Cu(mida)(SPHHGG)] and [Cu(mida)(HHHHHH)] as a function of pH indicate coordination of one histidyl donor at ca. 4.5, two in the range of pH 5-7, and two chelate ring attachments involving the terminal amino donor for SPHHGG or another histidyl donor of HHHHHH in the pH domain of 7-8 in agreement with the [PdII(mida)L] derivatives which form the two-chelate-ring attachment even at lower pH as shown by the 1H NMR methods.
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