the physical methods in inorganic chemistry (fall term, 2004) (fall term, 2005) department of...

The Physical Methods in Inorganic Chem

istry

(Fall Term, 2004) (Fall Term, 2005)

Department of ChemistryNational Sun Yat-sen University

無機物理方法（核磁共振部分）

Chemical Shift and J-Coupling

Chemical Shift

The surrounding electrons cause a shielding magnetic field at the nucleus

)1(00 BBBB s

Different environments cause different shieldings

))(1()( 00 rBBBrB s

(Representing different local chemical environments, Proctor and Yu, 1951)

Shielding Anisotropy (CSA)

B0

B0

)1(0 BB

Chemical shift anisotropy (CSA) tensor

In liquids, CSA is averaged out by rapid molecular tumbling; in solids, CSA is kept.

Electron clouds are seldomspherically symmetrical. Theyare anisotropic in almost all molecules.

Oriented Molecules

B0

Oriented Single Crystals

B0

Powder (Polycrystalline Solid)

B0

Chemical Shift Tensor

Anti-shielding Is Possible

))(1()( 00 rBBBrB s

Some proton chemical shifts

ref Reference shift

Most shielded

Least shielded

Type of Proton Structure Chemical Shift, ppmCyclopropane C3H6 0.2

Primary R-CH3 0.9

Secondary R2-CH2 1.3

Tertiary R3-C-H 1.5

Vinylic C=C-H 4.6-5.9

Acetylenic triple bond,CC-H 2-3

Aromatic Ar-H 6-8.5

Benzylic Ar-C-H 2.2-3

Allylic C=C-CH3 1.7

Fluorides H-C-F 4-4.5

Chlorides H-C-Cl 3-4

Bromides H-C-Br 2.5-4

Iodides H-C-I 2-4

Alcohols H-C-OH 3.4-4

Ethers H-C-OR 3.3-4

Esters RCOO-C-H 3.7-4.1

Esters H-C-COOR 2-2.2

Acids H-C-COOH 2-2.6

Carbonyl Compounds H-C-C=O 2-2.7

Aldehydic R-(H-)C=O 9-10

Hydroxylic R-C-OH 1-5.5

Phenolic Ar-OH 4-12

Enolic C=C-OH 15-17

Carboxylic RCOOH 10.5-12

Amino RNH2 1-5

Carbon-13 Chemical Shifts

Carbon-13* Environment

Chemical ShiftRange (ppm)

(CH3)2C*O -12

CS2 0

CH3C*OOH 16

C6H6 65

CHCl=CHCl (cis) 71

CH3C*N 73

CCl4 97

dioxane 126

C*H3CN 196

CHI3 332

Phosphorous-31 Chemical Shifts

Phosphorous-31 Environment

Chemical ShiftRange (ppm)

PBr3 -228

(C2H5O)3 P -137

PF3 -97

85% phosphoric acid 0

PCl5 80

PH3 238

P4 450

Compound

Chemical Shift (ppm)Relative to 85% H3PO4

PMe3 -62

PEt3 -20

PPr(n)3 -33

PPr(i)3 +19.4

PBu(n)3 -32.5

PBu(i)3 -45.3

PBu(s)3 +7.9

PBu(t)3 +63

PMeF2 245

PMeH2 -163.5

PMeCl2 +192

PMeBr2 +184

PMe2F +186

PMe2H -99

PMe2Cl -96.5

PMe2Br -90.5

Phosphorous (III) Chemical Shift Table (from Bruker Almanac 1991)

Phosphorous (V) Chemical Shift Table (from Bruker Almanac 1991)

CompoundChemical Shift (ppm)Relative to 85% H3PO4

Me3PO +36.2

Et3PO +48.3

[Me4P]+1 +24.4

[PO4]-3 +6.0

PF5 -80.3

PCl5 -80

MePF4 -29.9

Me3PF2 -158

Me3PS +59.1

Et3PS +54.5

[Et4p]+1 +40.1

[PS4]-3 +87

[PF6]-1 -145

[PCl4]+1 +86

[PCl6]-1 -295

Me2PF3 +8.0

Fluorine-19 Chemical Shifts

Fluorine-19 Environment

Chemical ShiftRange (ppm)

UF6 -540

FNO -269

F2 -210

bare nucleus 0

C(CF3)4 284

CF3(COOH) 297

fluorobenzene 333

F- 338

BF3 345

HF 415

Nitrogen-14 Chemical Shifts

Nitrogen-14* Environment

Chemical ShiftRange (ppm)

NO2Na -355

NO3- (aqueous) -115

N2 (liquid) -101

pyridine -93

bare nucleus 0

CH3CN 25

CH3CONH2 (aqueous) 152

NH4+ (aqueous) 245

NH3 (liquid) 266

B-11 Chemical Shift

Factors Affecting Chemical Shift

• Temperature

• Solvents (pH, concentration)

• Pressure

Major Contributions To CS

)(0 rBE

Applications of Chemical Shift

Ap

plicatio

ns o

f Ch

emical S

hift

http://www.bmrb.wisc.edu/data_access/outlier_selection_grid.html

Applications of Chemical Shift

Applications of Chemical Shift

Relaxation, dynamics

Solid state NMR

CS Imaging

……

Story Goes On

Indirect Dipolar Interaction (J-Coupling)

N

SN

S

Interaction between spins mediated by electrons around them.J-coupling is usually much smaller than direct dipolar coupling.

J-CouplingNMR/I

Homonuclear system

A Heteronuclear System AX System

X

X

A X

AXJ AXJ

11 32: :1 1: :nn nnn CC C C

1 2 1: : : : :1 1mmmmC C C

Spin A:

Spin B:

00000…000

10000…000

11111…101

11111…111

11111…110

01000…000

00100…000

…

11000…000

01100…000

00110…000

…

1=“up”0=“down”

General Cases of Two-Site Homonuclear Systems000…00

100…00

111…01

111…11

111…10

010…00

001…00

…

110…00

011…00

0011..00

…

Spin BSpin A

Exercise: Who are They?

ABC System

Equivalent Spins

Coupled with Quadrupolar Spins

Strong Coupling and Quantum Mechanical Treatment

Example

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Ha

Hb

Ｈｃ

Ha（Ｈｏｙｅ）

Ａｎａｌｙｓｉｓ

Ａｎａｌｙｓｉｓ

Ｈｃ

Ｈｄ

Ｈｄ

Ｒｅｓｕｌｔ

Ｒｅｓｕｌｔ

Karplus Equation

Karplus Equation showing the relationship between the observed couplingconstant and the φ(=θ-135o) angle. Note that unique solutions are obtained only for J > 8 Hz and J <5 Hz .

Φ

Karplus Equations

Karplus Equations3JH-C-C-H = 10 cos2 for 0 900, and3JH-C-C-H = 12 cos2 for 90 1800

Typical J-coupling constants• 3JCOCH Mulloy et al. Carbohydr. Res. 184 (1988) 39-46 • Tvaroska et al. Carbohydr. Res. 189 (1989) 359-362 • Anderson et al. J. Chem. Soc., Perkin 2 (1994) 1965-1967 • 3JCOCC B. Bose et al. J. Am. Chem. Soc. 120 (1998) 11158-11173 • Q. Xu and A. Bush Carbohydr. Res. 306 (1998) 335-339 • M.J. Milton et al. Glycobiology 8 (1998) 147-153 • 3JCCCH R. Aydin & H. Günther Mag. Reson. Chem. 28 (1990) 448-4

57 • A. de Marco et al. Biochemistry 18 (1979) 3847- • 3JPOCH Lankhorst et al. J. Biomol. Struct. Dyn. 1 (1984) 1387-1405 • 3JCCOP Lankhorst et al. J. Biomol. Struct. Dyn. 1 (1984) 1387-1405 • 3JHNCH S. Ludvigsen et al. J. Mol. Biol. 217 (1991) 731- A. Pardi et

al. J. Mol. Biol. 180 (1985) 741- • V.F. Bystrov， Prog. NMR Spectrosc. 10 (1976) 41- • 3JCNCH L.-F. Kao et al. J. Am. Chem. Soc. 107 (1985) 2323- 3JCNC

C L.-F. Kao et al. J. Am. Chem. Soc. 107 (1985) 2323- • 3JHCOH R.R. Fraser et al. Can. J. Chem. 47 (1969) 403-409

Applying the Karplus Equation

Applying the Karplus Equation

Long Range Coupling

Amino Acids

Amino Acid, Name, Abbr. R =

Alanine, ala,A CH3-

Arginine, arg,R H2N-C(=NH2+)-, NH-(CH2)3-

Asparagines,asn,N H2NC(O)CH2-

Aspartic acid, asp,D HOOC-CH2-

Cysteine, cys,C HS-CH2-

Glutamic acid, glu,E HOOC-(CH2)2-

Glutamine, gln,Q H2NC(O)CH2-, CH2-

Glycine, gly,G H-

Histidine, his,H

Isoleucine, ile,ICH3CH2-

CH(CH3)-

Leucine, leu,L (CH3)2CHCH2-

Lysine, lys,K +H3N(CH2)4-

Methionine, met,M CH3SCH2CH2-

Phenylalanine,phe,F Ph-CH2-

Praline, pro,P

Serine, ser,S HOCH2-

Threonine,thr,T CH3CH(OH)-

Tryptophan,trp,W

Tyrosine,tyr,Y HO-Ph-CH2-

Valine,val,V (CH3)2CH-

Summary of one-bond heteronuclear couplings along the polypeptide chain utilized in 3D and 4D NMR experiments

Structure of an A-U (top) and a C-G(bottom) Watson-Crick base pair. Notice that in eachcase, there is a single N-H ... N hydrogen bond. Scalarcoupling across this bond was determined to beapproximately 6.3 Hz for the GC bp and 6.7 Hz for theAU bp. Non-Watson Crick bp schemes (such asHoogsteen) contain different hydrogen bonds that can bedistinguished from traditional Watson-Crick.

(CH3)2CH

(CH3)2CH

Coupled

Decoupled

Varian parameters: dn, dm, dmm, dpwr

C-H Coupling and 13C Broadband Decoupling

13C-1H Coupling and 13C Broadband Decoupling

Selective Decoupling of 1H-1H

Selective Decoupling of 1H-1H