cyclic tetranuclear and hexanuclear palladium(ii) complexes and their host-guest chemistry

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Cyclic Tetranuclear and Hexanuclear Palladium(II) Complexes and Their Host-guest Chemistry

Judith A. Walmsley,* Shourong Zhu, Antonio Matilla, Tiffanee G. Donowick, Jessica E. Cramp, Jose Manuel Tercero, and Tatyana Dalrymple

Inorg. Chem. 2007, 46, 9945-9953

2Mirkin, C. A. et al. Angew. Chem. Int. Ed. 2001, 40, 2022-2043

Supramolecular Coordination Chemistry

Hydrogen bonding

Metal-ligand coordination

π-π stacking

Eletrostatic interactions

van der Waals forces

Hydrophobic interactions

Hydrophilic interactions

etc.

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Selective Formation of Different Geometric Structures by Appropriate Choice of Corner and Bridging Units

Kaiser, A.; Baeuerle, P. Top. Curr. Chem. 2005, 249, 127-201

4

Extraction of Hydrophobic Species into a Water-Soluble Synthetic Receptor

Hooley, R. J.; Van Anda, H. J.; Rebek, J., Jr. J. Am. Chem. Soc. 2007, 129, 13464-13473

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Molecular Necklace: Quantitative Self-Assembly ofa Cyclic Oligorotaxane from Nine Molecules

Whang, D.; Park, K.-M.; Heo, J.; Ashton, P.; Kim, K. J. Am. Chem. Soc. 1998, 120, 4899-4900

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Selective Formation of Different Geometric Structures by Appropriate Choice of Corner and Bridging Units

Kaiser, A.; Baeuerle, P. Top. Curr. Chem. 2005, 249, 127-201

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Structure of Guanine, Guanosine, and Guanosine 5’-monophosphate

(guanosine 5’-monophosphate)

Walmsley, J. A. et al. Inorg. Chim. Acta 2004, 357, 411-420

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Proposed Coordination Process of Pd(en)2+ with 5’GMP

Walmsley, J. A. et al. Inorg. Chim. Acta 2004, 357, 411-420

9Figure 1. Structure of [Pd(en)(5’GMP)]4

Pd(en)-5’GMP SystemNa2(5’GMP)

8.20

5.95

8.55

6.55

AA’BB’ multipletsinglet

N

N1N7

N

O

NH2

H8

H1'H4'OH OH

H3' H2'

OOPHO

O

O-

PdPd

H2N

NH2

A

B

A'B'

H2N

H2N

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Figure 2. 1H NMR spectra in D2O at pD 5.4 and 25 °C; (A) [Pd(en)-(5’GMP)]4 (20 mM total Pd(II)); (B) mixture of [Pd(en)(5’GMP)]4 and {-[Pd(en)(5’GMP)]6-DSS} (20 mM DSS and 20 mM total Pd(II)); ‘r’ stands for hexamer host-guest complex, ‘u’ stands for free guest ion.

[Pd(en)(5’GMP)]4 with DSS Guest

Sodium 3-(trimethylsilyl)-1-propanesulfonate (DSS)

-2.76

β-(CH2) 1.19, 1.09 ppm

(Δδ=0.4)

γ-(CH2) -0.91, -1.06 ppm

(Δδ=1.4)

SiH3C

CH3

CH3

(CH2)3 S

O

O

ONa

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Figure 4. Determination of Pd(en)(5’GMP)/DSS ratio in D2O at pD 5.4 by 1H NMR integrated intensity of the H1’ of host [Pd(en)(5’GMP)]6 and methyl protons of guest DSS; 10 mM total Pd(II) plus variable amounts of DSS.

Determined Pd(en)(5’GMP)/DSS ratio by 1H NMR

slope = 5.9 ± 0.4, 6.0 ± 0.3

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Figure 3. 31P NMR of 30 mM Pd(en)(5’GMP) in D2O (30 mM total Pd-(II)) with two different concentrations of DSS, pD 5.5; single line at 1.65 ppm is tetramer and two lines at 1.35-1.45 ppm are hexamer with DSS guest.

31P NMR of Pd(en)(5’GMP)/DSS in D2O

tetramer

hexamer

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Nuclear Overhauser Effect SpectroscopY

• American physicist Albert Overhauser who hypothesized it in the early 1950s. The phenomenon was demonstrated by C. P. Slichter and T. R. Carver in 1953.

• Nuclear Overhauser Effect (NOE) arises throughout radio frequency saturation of one spin, the effect causes the perturbation via dipolar interactions with further nucleus spins.

• NOESY spectra provide information about protons that are 5 Angstroms or less apart in space. The information is through space and not through bond.

14Figure 5. Partial 1H NOESY spectrum of [Pd(en)(5’GMP)]n (19 mM total Pd(II)) with 5 mM DSS in D2O at pD 5.7 and 25 °C.

Partial 1H NOESY Spectrum of [Pd(en)(5’GMP)]n with DSS Guest in D2O

H1’

H8

H8

H1’

H2’, H3’

N

NN

N

O

NH2

H8

H1'H4'OH OH

H3' H2'

OOPHO

O

O-

Pd(en)(en)Pd

methyl group

SiH3C

CH3

CH3

(CH2)3 S

O

O

O-

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Figure 6. (A) Proposed structure for the hexamer. The 5’GMP units are alternately pointing up and down around the ring. (B) Schematic drawing of [Pd(en)(5’GMP)]6 with DSS guest. The oval represents the Pd(en)-(guanine) and the vertical solid, and wavy lines represent the ribose group. Water molecules may mediate H-bonding between phosphate anions and between phosphate and sulfonate groups.

Proposed Structure for [Pd(en)(5’GMP)]6 Hexamer with DSS Guest

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pH 4.0 bonding of DSS was first observed

pH 5.0-5.5 reached a maximum

pH 6.0 decreasing

pH 7.7 only a small fraction of the DSS was bonded as host

NH

N

N

O

NH2N

O

H

HHHHOH

OPHO

O

OH

N

N

N

O

NH2N

O

H

HHHHOH

OPHO

O

O-

(en)Pd Pd(en)

N

N

N

O

NH2N

O

H

HHHHOH

OP-O

O

O-

(en)Pd Pd(en)

low pH

pH 5.0-6.0

pH 6.5

Strong pH Dependence of Host-guest Formation

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Figure 7. 1H NMR spectra of Pd(en)(5’GMP) (20 mM total Pd(II)) and t-butanol in D2O at pD 5.4 and 25 °C. The ‘u’ stands for the resonance from methyl protons of free t-butanol, and ‘r’ stands for methyl protons of guest or H8 and H1’ of hexamer.

1H NMR Spectra of Pd(en)(5’GMP)with t-Butanol Guest in D2O

Pd / t-butanol ratio is 5.9 ± 0.7

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1H NOESY Spectrum of [Pd(en)(5’GMP)]n with t-Butanol Guest in D2O

N

NN

N

O

NH2

H8

H1'H4'OH OH

H3' H2'

OOPHO

O

O-

Pd(en)(en)Pd

H1’

H8

t-BuOH methylu r

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Figure 8. 1H NMR resonances of i-butanol as guest in [Pd(en)(5’GMP)]6 in D2O at pD 5.4 and 26 °C; (20 mM total Pd(II) and 10 mM total i-butanol).

1H NMR Spectra of Pd(en)(5’GMP)with iso-butanol Guest in D2O

iso-butanol

heptet

two doubletsequal intensityJ = 7.0 Hz

r

r

r

uu

H8

H1’

u

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1H NMR Spectrum of Pd(en)(5’GMP)with 2-Propanol Guest in D2O

r uu

r

2-PrOHr

2-PrOHu

H8

H1’

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1H NMR Spectrum of Pd(en)(5’GMP)with TMS Guest in D2O

CH3

SiH3C CH3

CH3

tetramethylsilane (TMS)

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Crystal Structure of [Pd(dapol)Cl2]

Figure 10. ORTEP drawing of [Pd(dapo)Cl2] with the atomic numbering scheme; displacement ellipsoids are shown at the 50% level.

Table 4. Selected Bond Lengths (Å) and Angles (deg) for [Pd(dapol)Cl2]

1,3-diamino-2-propanol (dapol)

H2N NH2

OH

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Figure S12. Packing diagram of [Pd(dapol)Cl2]; Color code: Pd (green), Cl (yellow), C (black), N (blue), O (red), H (white).

Packing Diagram of [Pd(dapol)Cl2]

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Figure 9. 1H NMR spectra in D2O at 25 °C. (A) 25 mM Pd(dapol)-(5’GMP), pD 5.4 (25 mM total Pd(II)); (B) mixture of (A) and [Pd(dapol)-(5’GMP)]6-2-PrOH (20 mM total Pd(II), 1.5 mM 2-PrOH), pD 5.8. ‘react’ refers to the host-guest complex.

1H NMR Spectra of Pd(dapol)(5’GMP)with 2-Propanol Guest in D2O

1,3-diamino-2-propanol (dapol)

H2N NH2

OH

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Chemical Shifts of Methyl Protons of Guests in [Pd(diamine)(5’GMP)]n

Table 2. Chemical Shifts of Methyl Protons of Guests in [Pd(diamine)(5’GMP)]na

TSP = Sodium 3-(trimethysilyl)propionate-d4

SiH3C

CH3

CH3

(CH2)3 S

O

O

O-CH3

SiH3C CH3

CH3

O

NaO Si

DD

D D

DSS = Sodium 3-(trimethylsilyl)-1-propanesulfonate TMS = Tetramethylsilane

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Table 3. K’assoc and Thermodynamic Parameters of [Pd(en)(GMP)]6 Host-Guest Complexes at 26 °C

Association Constants of [Pd(en)(GMP)]6

Host-Guest Complexes

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Conclusions

1. Upon the introduction of a small organic molecule with hydrophobic interaction sites, the tetramers spontaneously expanded to form a hexamer with one guest molecule strongly incorporated into the central cavity.

2. We feel that the ease with which the tetramer expanded to the hexamer might be related to unfavorable steric interactions of the 5’GMP at the N7-Pd-N7 corners in the tetramer, rendering the expansion in the presence of a templating agent enegetically favorable.

3. The guests can be cationic, anionic, or neutral with a high degree of hydrophobic character. They bind strongly to the host in a 1:1 mole ratio, are in slow chemical exchange with uncomplexed guest molecules, and exhibit very large upfield chemical shifts (2.5-3.0 ppm) in the NMR spectra for the most highly affected protons.