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