A Theoretical Investigation of 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups

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1 A Theoretical Investigation of 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups İrfan Şaka and Azmi Gençten Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139, Samsun, Turkey Reprint requests to A. G.; Fax: ; gencten@omu.edu.tr Z. Naturforsch. 63a, (2008); received September 4, 2007 There exists a variety of multiple-pulse NMR experiments for spectral editing of complex molecules in solution. Maximum quantum correlation NMR (MAXY NMR) spectroscopy is one of the techniques for distinguishing CH n groups by editing 1 H NMR spectra. Spectral assignments of 2D homonuclear J-resolved NMR spectroscopy become too difficult, due to complex overlapping spectra. In order to overcome this problem a new technique called 2D MAXY-JRES NMR spectroscopy, which is the combination of MAXY NMR and homonuclear J-resolved NMR spectroscopy, is used. In this study, product operator description of 2D MAXY-JRES NMR spectroscopy is performed for IS n I S m (I = I = 1 2 ; S = S = 1; n = 1,2,3; m = 1,2) multi-spin systems. Experimental suggestions are made and simulated spectra are presented for the 2D MAXY-JRES NMR experiment. Therefore, it is shown that 2D MAXY-JRES NMR spectroscopy can be used to distinguish CD, CD 2 and CD 3 groups from each other in CD n CD m groups. Key words: NMR; MAXY-JRES; Product Operator Formalism; Spin Introduction There exists a large number of homo- and heteronuclear multiple-pulse 1D, 2D and 3D nuclear magnetic resonance (NMR) experiments. Maximum quantum correlation (MAXY) NMR spectroscopy is one of the techniques for distinguishing CH n groups by editing 1 H NMR spectra [1 7]. 13 C NMR spectroscopy is also widely used in editing methods such as DEPT [8] and SEMUT [9]. Editing and selective detection methods for 1 H NMR spectroscopy are reviewed in [10]. In homonuclear J-resolved NMR spectroscopy, the chemical shift and spin-spin coupling parameters are resolved along the two different axes for the same kind of coupled nuclei such as 1 H. Sometimes, spectral assignments of 2D homonuclear J-resolved NMR spectroscopy become too difficult, due to complex overlapping spectra. In order to overcome this problem a new technique called 2D MAXY- JRES NMR spectroscopy, which is the combination of MAXY and homonuclear J-resolved NMR spectroscopy, is used [3]. This technique is used to distinguish CH n CH m groups in complex samples such as biological fluids [3]. 2 H NMR spectroscopy became a powerful technique for different applications such as deuterium labelling and structure elucidation [11]. Therefore, 2D MAXY-JRES NMR spectroscopy can be also used for the identification of CD n CD m groups in complex samples. As NMR is a quantum mechanical phenomenon, nuclear spin systems can be treated by quantum mechanical methods. The product operator formalism, as a simple quantum mechanical method, has been developed for the analytical description of multiple-pulse NMR experiments of weakly coupled spin systems in liquids having spin-1/2 and spin-1 nuclei [12 22]. In this formalism, the spin operators themselves and their direct products, called product operators, are used. By using the product operator theory, SEMUT NMR spectroscopy is applied to CD n groups [23]. Experimental and theoretical investigations of 13 CDEPTNMR spectroscopy of CD n systems are presented in [24]. For CH n and CD n groups, the product operator theory of a 2D DEPT J-resolved NMR experiment is investigated [25, 26]. Product operator descriptions of MAXY and MAXY-HMQC NMR experiments of CD n groups are also reported in our recent studies [27, 28]. The product operator theory for spin-3/2 and its application to 2D J-resolved NMR spectroscopy is reported [29]. For spin systems having spin-3/2 nuclei, / 08 / $ c 2008 Verlag der Zeitschrift für Naturforschung, Tübingen

2 340 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups by using the product operator formalism, theoretical investigations of 3D J-resolved, DEPT, SEMUT, INEPT and RINEPT NMR experiments are also presented [30 32]. The product operator theory of high resolution solution state double quantum spectroscopy of two spin-1 AX systems are investigated [21, 33, 34]. By using the product operator theory in NMR experiments, experimental results can be confirmed and also new experimental suggestions can be made [19, 23]. In the present study experimental suggestions are made. In the present study, first, evolutions of some product operators under the homonuclear scalar spin-spin coupling Hamiltonian for a SS (S = 1, S = 1) spin system are obtained. Then, by using the product operator formalism, theoretical results are obtained for the 2D MAXY-JRES NMR experiment of IS n I S m (I = I = 1/2; S = S = 1; n = 1,2,3; m = 1,2) multispin systems. By using the obtained theoretical results, experimental suggestions are presented, and simulated spectra of various groups are obtained for the 2D MAXY-JRES NMR experiment. To the best of our knowledge, this will be the first product operator description of a 2D MAXY-JRES NMR experiment of CD n CD m groups. As a result, it is shown that one can perform this experiment to distinguish CD, CD 2 and CD 3 groups in CD n CD m systems. 2. Theory The product operator theory is the expansion of the density matrix operator in terms of matrix representation of angular momentum operators for individual spins. For the IS (I = 1/2, S = 1) spin system, four Cartesian spin angular momentum operators for I = 1/2, E I, I x, I y, I z, and nine Cartesian spin angular momentum operators for S = 1, E S, S x, S y, S z, Sz 2, [S x,s z ] +, [S y,s z ] +, [S x,s y ] +, (Sx 2 S2 y ), can be easily found [35]. So, 4 9 = 36 product operators for the IS (I = 1/2, S = 1) spin system are obtained with direct products of these angular momentum operators. For the IS (I = 1, S = 1) spin system there will be 9 9 = 81 product operators. Time dependence of the density matrix is governed by the Liouville-von Neumann equation: dσ dt = ī [σ,h], (1) h where [σ,h] is the commutator of the density matrix, σ, and the Hamiltonian, H. When the Hamiltonian is time-independent, the solution of the (1) is σ(t) =exp( iht)σ(0) exp(iht), (2) where H is the total Hamiltonian which consists of radiofrequency (r. f.) pulse, chemical shift and spin-spin coupling Hamiltonians, and σ(0) is the density matrix at t = 0. After employing the Hausdorff formula [16] exp( iht)a exp(iht)=a (it)[h, A] + (it)2 2! [H,[H,A]] (it)3 3! [H,[H,[H,A]]]+, (3) evolutions of product operators under the r. f. pulse, chemical shift and spin-spin coupling Hamiltonians can be easily obtained [12, 16, 18]. A complete product operator theory for the IS (I = 1/2, S = 1) spin system and its application to the DEPT-HMQC NMR experiment is presented in our recent study [36]. For the IS (I = 1, S = 1) spin system the evolutions of some product operators under the spin-spin coupling Hamiltonian (H J = 2πJI z S z ) are known; they are given as follows [21, 33, 34]: I x S y H J t 1 2 I xs y (c 2J + 1)+ 1 2 I yzs xz (c 2J 1) I z S 2 x I z S 2 y (I ys yz I xz S x )S 2J, H J t 1 2 I zs 2 x (c 4J + 1) 1 2 I zs 2 y (c 4J 1) I2 z S xys 4J, H J t 1 2 I zs 2 y (c 4J + 1) 1 2 I zs 2 x (c 4J 1) 1 2 I2 z S xys 4J. (4) (5) (6) In these equations, I yz =[I y,i z ] +, I xz =[I x,i z ] +, S xz = [S x,s z ] +, S yz =[S y,s z ] +,ands xy =[S x,s y ] +. For this spin system the evolutions of some other product operators under the spin-spin coupling Hamiltonian are obtained and presented in the following section. At any time during the experiment, the ensemble averaged expectation value of the spin angular momentum, e. g. for I y,is I y = Tr[I y σ(t)], (7) where σ(t) is the density matrix operator calculated from (2) at any time. As I y is proportional to the magnitude of the y-magnetization, it represents the signal

3 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups 341 Fig. 1. Pulse sequence of the 2D MAXY- JRES NMR experiment [3]. detected on the y-axis. So, in order to estimate the free induction decay (FID) signal of a multiple-pulse NMR experiment, the density matrix operator should be obtained at the end of the experiment. 3. Evolutions of Some Product Operators under the Spin-Spin Coupling Hamiltonian As the homonuclear spin-spin coupling occurs between two spin-1 nuclei (S and S spin) during t 1 in the 2D MAXY-JRES NMR experiment, we need to obtain the evolutions of some product operators under the homonuclear scalar spin-spin coupling Hamiltonian, H(S S )=2πJ SS S z S z. By using the Hausdorff formula, evolution of the Sx 2 product operator under the spin-spin coupling Hamiltonian can be obtained as S 2 x H SS t exp( 2iπJS z S z t)s2 x exp(2iπjs zs z t) = Sx 2 (i2πjt)a(1)+(i2πjt)2 A(2) 2! (i2πjt)3 A(3)+..., 3! (8) A(1)=[S z S z,s x], 2 (9) A(2)=[S z S z,a(1)], (10) A(3)=[S z S z,a(2)]. (11) Using commutation relations and Si n Sn 2 i (n 3) for spin-1, Sx 2 H SS t Sx 2 1 { } (4πJt) 2 (Sx 2 2 2! S2 y )S 2 z { (4πJt)[Sx,S y ] + S z } (4πJt)3 [S x,s y ] + S z 3! +... (12) is obtained. In order to get the generalized form for the evolution of the Sx 2 product operator under the spinspin coupling Hamiltonian, some additions and subtractions can be made; then one obtains the following Table 1. Evolutions of some product operators under the spin-spin coupling Hamiltonian (H SS = 2πJ SS S z S z). S xz = [S x,s z ] +, S yz =[S y,s z ] +,ands xy =[S x,s y ] +. Product operator Evolution of product operator under the spin-spin coupling Hamiltonian S 2 x S 2 x (S2 x S 2 y)s 2 z (c 4J 1)+ 1 2 S xys zs 4J S 2 y S 2 y 1 2 (S2 x S 2 y)s 2 z (c 4J 1) 1 2 S xys zs 4J S xz S xz + S xz S 2 z (c 2J 1)+S yz S zs 2J S yz S yz + S yz S z 2(c 2J 1) S xz S z s 2J S xy S xy + S xy S z 2(c 4J + 1) (Sx 2 S2 y )S z s 4J shorthand notation form: S 2 x 2πJS z S zt Sx (S2 x Sy)S 2 z 2 (c 4J 1)+ 1 2 S xysz s 4J. (13) Here, and in the following equations, S xz =[S x,s z ] +, S yz =[S y,s z ] +, S xy =[S x,s y ] +, c nj = cos(nπjt 1 ) and s nj = sin(nπjt 1 ). For the remaining product operators, the similar procedure is applied and the obtained results are given in Table 1. Similar evolutions can be easily obtained for the product operators S x 2, S y 2, S xz, S yz,ands xy under the scalar spin-spin coupling Hamiltonian. 4. Results and Discussion In this section, the analytical descriptions of 2D MAXY-JRES NMR spectroscopy of IS n I S m (I = I = 1 2 ; S = S = 1; n = 1,2,3; m = 1,2) multi-spin systems are presented by using the product operator theory. This section is divided into two subsections. In the first one, theoretical results for the analytical description of the 2D MAXY-JRES experiment are obtained; in the second one, experimental suggestions and simulated spectra for several CD n CD m groups are presented Product Operator Theory For the product operator description of the 2D MAXY-JRES NMR experiment, the pulse sequence,

4 342 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups Table 2. Evolutions of nine angular momentum operators under the r. f. pulse Hamiltonian (θs φ )atx- andy-axes for S = 1 [36]. c nθ = cos(nθ) and s nθ = sin(nθ). Angular momen- φ Evolution under the tum operator r. f. pulse Hamiltonian S x x S x S y x S y c θ + S z s θ S z x S z c θ S y s θ [S x,s y ] + x [S x,s y ] + c θ +[S x,s z ] + s θ [S x,s z ] + x [S x,s z ] + c θ [S x,s z ] + s θ [S y,s z ] + x [S y,s z ] + c 2θ (Sy 2 S2 z )s 2θ Sx 2 x Sx 2 Sy 2 x 1 2 Sy(c 2 2θ + 1) 1 2 S2 z (c 2θ 1)+ 1 2 [S y,s z ] + s 2θ Sz 2 x 1 2 Sz 2 (c 2θ + 1) 1 2 S2 y(c 2θ 1) 1 2 [S y,s z ] + s 2θ S x y S x c θ S z s θ S y y S y S z y S z c θ + S x s θ [S x,s y ] + y [S x,s y ] + c θ +[S y,s z ] + s θ [S x,s z ] + y [S x,s z ] + c 2θ +(Sx 2 Sz 2 )s 2θ [S y,s z ] + y [S y,s z ] + c θ +[S x,s y ] + s θ Sx 2 y S 2 x 2 (c 2θ + 1) S2 z 2 (c 2θ 1) 1 2 [S x,s z ] + s 2θ Sy 2 y Sy 2 Sz 2 y S 2 z 2 (c 2θ + 1) S2 x 2 (c 2θ 1)+ 1 2 [S x,s z ] + s 2θ Table 3. Evolutions of nine angular momentum operators under the chemical shift Hamiltonian (Ω S S z )fors = 1 [36]. c ns = cos(nω S t) and s ns = sin(nω S t). Angular momentum Evolution under the operator chemical shift Hamiltonian S x S x c S + S y s S S y S y c S S x s S S z S z [S x,s y ] + [S x,s y ] + c 2S +(Sy 2 Sx)s 2 2S [S x,s z ] + [S x,s z ] + c S +[S y,s z ] + s S [S y,s z ] + [S y,s z ] + c S [S x,s z ] + s S Sx S2 x (c 2S + 1) 1 2 S2 y (c 2S 1)+ 1 2 [S x,s y ] + s 2S Sy S2 y (c 2S + 1) 1 2 S2 x (c 2S 1) 1 2 [S x,s y ] + s 2S Sz 2 Sz 2 illustrated in Fig. 1, is used [3], where the density matrix operator at each stage of the experiment is labelled with numbers. 13 C is treated as spins I and I,and 2 H(D) as spins S and S in Figure 1. In the pulse sequence, the optimum value of is 1/(2J IS ), is a short compensation delay, t 1 is the incremented evolution delay during homonuclear spin-spin coupling, which takes place between S and S spins and t 2 is the acquisition time for S and S spins along y-axes [3]. Starting from the density matrix operator at thermal equilibrium, one should apply the required Hamiltonians during the pulse sequence and obtain the density matrix operator at the end of the experiment. For Table 4. Evolutions of 32 product operators under the spinspin coupling Hamiltonian (2πJI z S z )oftheis (I = 1/2, S = 1) spin system [36]. c nj = cos(nπjt) and s nj = sin(nπjt). Product Evolution under the spin-spin operator coupling Hamiltonian I x I y S z s 2J + I x (1 + Sz 2 (c 2J 1)) I y I x S z s 2J + I y (1 + Sz 2 (c 2J 1)) S x S x c J + 2I z S y s J S y S y c J 2I z S x S J I x S z I x S z c 2J + I y Sz 2 s 2J I y S z I y S z c 2J I x Sz 2 s 2J I z S x I z S x c J S ys J I z S y I z S y c J 1 2 S xs J I x S x I x S x c J + I y [S x,s z ] + s J I x S y I x S y c J + I y [S y,s z ] + s J I y S x I y S x c J I x [S x,s z ] + s J I y S y I y S y c J I x [S y,s z ] + s J I x Sz 2 I x Sz 2 c 2J + I y S z s 2J I y Sz 2 I y Sz 2c 2J I x S z s 2J I x Sy 2 I x Sy I xsz 2 (c 2J 1)+ 1 2 I ys z s 2J I y Sy 2 I y Sy I ysz 2 (c 2J 1)+ 1 2 I xs z s 2J Sx S2 x (c 2J + 1) 1 2 S2 y (c 2J 1)+I z [S y,s x ] + s 2J Sy S2 y(c 2J + 1) 1 2 S2 x(c 2J 1) I z [S y,s x ] + s 2J I z Sx I zsx(c 2 2J + 1) 1 2 I zsy(c 2 2J 1)+ 1 4 [S y,s x ] + s 2J I z Sy I zsy 2(c 2J + 1) 1 2 I zsx 2(c 2J 1) 1 4 [S y,s x ] + s 2J I x [S x,s z ] + I x [S x,s z ] + c J + I y S x s J I x [S y,s z ] + I x [S y,s z ] + c J + I y S y s J I y [S x,s z ] + I y [S x,s z ] + c J I x S x s J I y [S y,s z ] + I y [S y,s z ] + c J I x S y s J [S x,s z ] + [S x,s z ] + c J + 2I z [S y,s z ] + s J [S y,s z ] + [S y,s z ] + c J + 2I z [S x,s z ] + s J [S x,s y ] + [S x,s y ] + c 2J + 2I z (Sy 2 S2 x )s 2J I z [S x,s z ] + I z [S x,s z ] + c J S y,s z + s J I z [S y,s z ] + I z [S y,s z ] + c J [S x,s z ] + s J I z [S x,s y ] + I z [S x,s y ] + c 2J (S2 y S2 x )s 2J I x Sx 2 I x Sx I xsz 2(c 2J 1)+ 1 2 I ys z s 2J I y Sx 2 I y Sx I ysz 2 (c 2J 1) 1 2 I xs z s 2J this experiment, r. f. pulse, chemical shift and spinspin coupling Hamiltonians are applied. For I = I = 1 2 spins, evolutions of angular momentum operators under the r. f. pulse Hamiltonian are known [12, 22]. In the case of S = S = 1 spins, evolutions of 9 angular momentum operators under the r. f. pulse Hamiltonian were obtained in our previous study [36]. They are presented in Table 2. During t 2, the chemical shift Hamiltonian for angular momentum operators of S = S = 1 spins is applied. Their evolutions are presented in Table 3 [36]. During and, the spin-spin coupling Hamiltonians H J (I S)=2πJ IS I z S z and H J (I S )= 2πJ I S I zs z are applied to the IS (I = 1 2, S = 1) and

5 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups 343 I S (I = 1 2, S = 1) spin systems, respectively. For these spin systems, evolutions of 36 (or 40 in separated form) product operators under the spin-spin coupling Hamiltonian are known and given in Table 4 [36]. During t 1, the homonuclear spin-spin coupling Hamiltonian H J (S S )=2πJ SS S z S z is applied to the SS (S = 1, S = 1) spin system. Required evolutions are obtained in Section 3. For multi-spin systems, to follow these processes (applications of required Hamiltonians during the pulse sequence) by hand becomes too difficult. In order to overcome this problem a computer program is written in Mathematica for the present study. This program is used to obtain the density matrix operator at the end of the experiment for different spin systems. For the ISI S multi-spin system, the density matrix at thermal equilibrium is σ 0 = S z + S z.byusingthe computer program the following density matrices for each labelled point are obtained: σ 0 90 x(s,s ) S y S y σ 1, (14) 2πJ IS I z S z ( =1/(2J IS ))+2πJ σ I S I zs z ( =1/(2J I S )) 1 (15) 2I z S x + 2I z S x, 180 σ x(s,s )+90 x(i,i ) 2 2I y S x 2I ys x, (16) 2πJ IS I z S z ( =1/(2J IS ))+2πJ σ I S I zs z ( =1/(2J I S )) 3 2I x S xz + 2I xs xz, (17) σ 4 90 x(s,s ) 2I x S xy 2I x S xy σ 5, (18) σ 16 = Syc S s θ S yc Ss θ + S y S 2 z s θ + S 2 zs yc Ss θ S y S 2 z c 2J c S s θ S 2 zs yc 2Jc Ss θ + 2I x S xy c θ + 2I xs xyc θ + 2I x S xy S 2 z c θ + 2I xs xys 2 z c θ + 2I x S xy S 2 z c 4Jc θ + 2I x S xy S2 z c 4J c θ 2I x S 2 x S z s 4Jc 2S c θ 2I x S 2 x S zs 4J c 2Sc θ + 2I x S 2 y S z s 4Jc 2S c θ + 2I x S 2 y S zs 4 j c 2Sc θ + S x S zs 2J c S s θ + S z S xs 2Jc S s θ + S x s S s θ + S x s Ss θ S x S 2 z s Ss θ S 2 z S x s Ss θ + S x S 2 z c 2Js S s θ + S 2 z S x c 2J s Ss θ + S z S ys 2J s S s θ + S y S zs 2 js S s θ 2I x S xy S zs 4J s 2S c θ 2I xs xys z s 4 js 2S c θ, (19) where c nj = cos(nπj SS t 1 ), c nj = cos(nπj S S t 1), s nj = sin(nπj SS t 1 ), s nj = sin(nπj S S t 1), c ns = cos(nω S t 2 ), c ns = cos(nω S t 2), s ns = sin(nω S t 2 ), s ns = sin(nω S t 2), S xz =[S x,s z ] +, S yz =[S y,s z ] +, S xy =[S x,s y ] +, S xz = [S x,s z ] +, S yz =[S y,s z ] + and S xy =[S x,s y ] +. In the density matrix operator, only the terms with observable product operators are kept as they are the only ones that contribute to the signal on y-axis detection. Then the magnetization along the y-axis is proportional to S y + S y and M y (t 1 t 2 ) S y + S y = Tr[S yσ 16 ]+Tr[S yσ 16 ]. (20) Now it is necessary to obtain the Tr[S y O] and Tr[S yo ] values of observable product operators indicated by O and O. These trace values are calculated by a computer program in Mathematica and the results for several multi-spin systems are given in Tables 5 and 6. For example, trace of the S y product operator is calculated as Tr[S iy O]=Tr[S y S y ] = Tr[(E 1 S y E 1 E S ) (E 1 S y E 1 E S )] = 24. (21) By using Tables 5 and 6, S y + S y = 8(1+2c 2J)c S s θ 8(1+2c 2J )c S s θ (22) is obtained for the ISI S multi-spin system. This equation represents the FID signals of the 2D MAXY- JRES NMR experiment for the ISI S multi-spin system. There exist triplet signals with the same intensity distribution of 1 : 1 : 1 for both S and S spins at the coordinates (2J,Ω S ):(Ω S ):( 2J,Ω S ) and (2J,Ω S ):(Ω S ):( 2J,Ω S ), respectively. Another example can be the IS 2 I S multi-spin system. As one can guess, product operator calculations for this spin system will be more complicated than those of the ISI S multi-spin system. The product operator description of this spin system is provided in Appendix B. For the ISI S, IS 2 I S, IS 3 I S, IS 2 I S 2 and IS 3 I S 2 multi-spin systems, the trace values of the density matrix operators and their signal coordinates with the intensity distributions are given in Tables 7 and 8 for S and S spins, respectively. n i=1 Tr[S iyσ 16 ] + m j=1 Tr[S jy σ 16] values obtained for the ISI S, IS 2 I S, IS 3 I S, IS 2 I S 2 and IS 3 I S 2 multi-spin systems represent the FID signals of the 2D MAXY-JRES NMR experiment of CDCD, CD 2 CD, CD 3 CD, CD 2 CD 2 and CD 3 CD 2 groups,

6 344 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups Table 5. Results of the n i=1 Tr[S iyo] calculations for observable product operators of IS n I S m multi-spin systems (k = x,y,z; l = x,y,z; o = x,y,z; p = x,y,z). Spin system Product operators (O) n i=1 Tr[S iyo] 24 ISI S 16 IS 2 I S IS 3 I S IS 2 I S 2 IS 3 I S 2 S y S y S k 2 S 1y + S 2y S 1y (S2k 2 + S 2 k )+S 2y(S1k 2 + S 2 k ) S 1y S2k 2 S 2 I + S1k 2 S 2yS I 2 S 1y + S 2y + S 3y S 1y (S 2 2k + S2 3k + S 2 k )+S 2y(S 2 1k + S2 3k + S 2 k )+S 3y(S 2 1k + S2 2k + S 2 k ) S 1y (S2k 2 S2 3I + S2 2k S 2 I + S3k 2 S 2 I )+S 2y(S1k 2 S2 3I + S2 1k S 2 I + S3k 2 S 2 I )+S 3y(S1k 2 S2 2I + S2 1k S 2 I + S2k 2 S 2 I ) S 1y S2k 2 S2 3l S 2 o + S1k 2 S 2yS3l 2 S 2 o + S1k 2 S2 2l S 3yS o 2 S 1y + S 2y S 1y (S 2 2k + S 2 1k + S 2 2k )+S 2y(S 2 1k + S 2 1k + S 2 2k ) S 1y (S2k 2 S 2 1l + S2 2k S 2 2l + S 2 1k S 2 2l )+S 2y(S1k 2 S 2 1l + S2 1k S 2 2l + S 2 1k S 2 2l ) S 1y S 2 2k S 2 1l S 2 2o + S2 1k S 2yS 2 1l S 2 2o S 1y + S 2y + S 3y S 1y (S2k 2 + S2 3k + S 2 1k + S 2 2k )+S 2y(S1k 2 + S2 3k + S 2 1k + S 2 2k )+S 3y(S1k 2 + S2 2k + S 2 1k + S 2 2k ) S 1y (S2k 2 S2 3l + S2 2k S 2 1l + S2 2k S 2 2l + S2 3k S 2 1l + S2 3k S 2 2l + S 2 1k S 2 2l )+S 2y(S1k 2 S2 3l + S2 1k S 2 1l + S2 1k S 2 S 1k 2 S 2 2l )+S 3y(S1k 2 S2 2l + S2 1k S 2 1l + S2 1k S 2 2l + S2 2k S 2 1l + S2 2k S 2 2l + S 2 1k S 2 2l ) S 1y (S 2 2k S2 3l S 2 1o +S2 2k S2 3l S 2 2o +S2 2k S 2 S 3y (S 2 1k S2 2l S 2 1o + S2 1k S2 2l S 2 2o + S2 1k S 2 1l S 2 2o + S2 2k S 2 1l S 2 S 1y S 2 2k S2 3l S 2 1o S 2 2p + S2 1k S 2yS 2 3l S 2 1o S 2 2p + S2 1k S2 2l S 3yS 2 1o S 2 2p 2l + S2 3k S 2 1l + S2 3k S 2 2l + 1l S 2 2o +S2 3k S 2 1l S 2 2o )+S 2y(S1k 2 S2 3l S 2 1o +S2 1k S2 3l S 2 2o +S2 1k S 2 1l S 2 2o +S2 3k S 2 1l S 2 2o )+ 2o ) Table 6. Results of the m j=1 Tr[S jy O ] calculations for observable product operators of IS n I S m multi-spin systems (k = x,y,z; l = x,y,z; o = x,y,z; p = x,y,z). Spin system Product operators (O) n j=1 Tr[S jy O ] ISI S S y 24 Sk 2S 16 y S y 72 IS 2 I S (S1k 2 + S2 2k )S y 96 S1k 2 S2 2l S 32 y IS 3 I S IS 2 I S 2 IS 3 I S 2 S y (S1k 2 + S2 2k + S2 3k )S y (S1k 2 S2 2l + S2 1k S2 3l + S2 2k S2 3l )S y S1k 2 S2 2l S2 3o S y S 1y + S 2y (S 2 1k + S2 2k + S 2 2k )S 1y +(S2 1k + S2 2k + S 2 1k )S 2y (S 2 1k S2 2l + S2 1k S 2 2l + S2 2k S 2 2l )S 1y +(S2 1k S2 2l + S2 1k S 2 1l + S2 2k S 2 1l )S 2y S 2 1k S2 2l S 1y S 2 2o + S2 1k S2 2l S 2 1o S 2y S 1y + S 2y (S 2 1k + S2 2k + S2 3k + S 2 2k )S 1y +(S2 1k + S2 2k + S2 3k + S 2 1k )S 2y (S 2 1k S2 2l + S2 1k S2 3l + S2 2k S2 3l + S2 1k S 2 2l + S2 2k S 2 2l + S2 3k S 2 2l )S 1y +(S2 1k S2 2l + S2 1k S2 3l + S2 2k S2 3l + S2 1k S 2 1l + S2 2k S 2 1l + S 2 3k S 2 1l )S 2y (S 2 1k S2 2l S2 3o + S2 1k S2 2l S 2 2o + S2 1k S2 3l S 2 2o + S2 2k S2 3l S 2 2o )S 1y +(S2 1k S2 2l S2 3o + S2 1k S2 2l S 2 1o + S2 1k S2 3l S 2 1o + S2 2k S2 3l S 2 1o )S 2y S 2 1k S2 2l S2 3o S 1y S 2 2p + S2 1k S2 2l S2 3o S 2 1p S 2y respectively. The n i=1 Tr[S iyσ 16 ]+ m j=1 Tr[S jy σ 16] values for IS n I S m (I = I = 1 2 ; S = S = 1; n = 1,2,3; m = 1,2) multi-spin systems can be generalized as follows: n i=1 Tr[S iy σ 16 ]+ m j=1 Tr[S jyσ 16 ](IS n I S m)=

7 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups 345 Table 7. n i=1 Tr[S iyσ 16 ] values, signal coordinates and intensity distribution for S spins of various multi-spin systems. Spin system n i=1 Tr[S iyσ 16 ] Signal coordinate Intensity distribution ISI S 8(1 + 3c 2J )c S s θ (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) 1:1:1 IS 2 I S 16(1 + 2c 2J )c S (1 2c θ )s θ (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) 1:1:1 IS 3 I S 24(1 + 2c 2J )c S (1 2c θ ) 2 s θ (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) 1:1:1 IS 2 I S 2 16(1 + 2c 2J ) 2 c S (1 2c θ )s θ (4J,Ω S ) : (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) : ( 4J,Ω S ) 1:2:3:2:1 IS 2 I S 2 24(1 + 2c 2J ) 2 c S (1 2c θ ) 2 s θ (4J,Ω S ) : (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) : ( 4J,Ω S ) 1:2:3:2:1 Table 8. m j=1 Tr[S jy σ 16] values, signal coordinates and intensity distribution for S spins of various multi-spin systems. Spin system m j=1 Tr[S jy σ 16] Signal coordinate Intensity distribution ISI S 8(1 + 2c 2J )c S s θ (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) 1:1:1 IS 2 I S 8(1 + 2c 2J )2 c S s θ (4J,Ω S ) : (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) : ( 4J,Ω S ) 1:2:3:2:1 IS 3 I S 8(1 + 2c 2J )3 c S s θ (6J,Ω S ) : (4J,Ω S ) : (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) : ( 4J,Ω S ) : ( 6J,Ω S ) 1:3:6:7:6:3:1 IS 2 I S 2 16(1 + 2c 2J )2 c S (1 2c 2θ )s θ (4J,Ω S ) : (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) : ( 4J,Ω S ) 1:2:3:2:1 IS 3 I S 2 16(1 + 2c 2J )3 c S (1 2c 2θ )s θ (6J,Ω S ) : (4J,Ω S ) : (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) : ( 4J,Ω S ) : ( 6J,Ω S ) 1:3:6:7:6:3:1 Fig. 2. Plots of relative signal intensity of 2D 2 H MAXY-JRES NMR spectroscopy of IS n groups as functions of the selective pulse angle θ. 8n(1 + 2c 2J ) m c S (1 2c 2θ ) n 1 s θ 8m(1 + 2c 2J ) n c S (1 2c 2θ) m 1 s θ. (23) The n i=1 Tr[S iyσ 16 ]+ m j=1 Tr[S jy σ 16] values can be normalized by multiplication of the first term with 36/(8nmTr(E)) and the second term with 36/(8mnTr(E )). HereE and E is the unity product operator of the corresponding spin system. So, normalized FID values can be also generalized as follows: n i=1 Tr[S iy σ 16 ]+ m j=1 Tr[S jyσ 16 ]= 1 1 m 3 n+m 2 (1 + 2c 2J) m c S (1 2c 2θ ) n 1 s θ (24) 1 1 n 3 n+m 2 (1 + 2c 2J) n c S (1 2c 2θ) m 1 s θ. The plots of these normalized and generalized functions of 2D 2 H MAXY-JRES NMR spectroscopy are presented in Figure 2. As can be seen in this figure, the relative signal intensities of the IS, IS 2 and IS 3 groups vary as functions of the selective pulse angle θ Experimental Suggestions and Simulated Spectra The real relative signal intensities of the 2D MAXY- JRES NMR experiment for CD n groups are given in Table 9. As can be seen in Table 9 and in Fig. 2, for θ = 195 or 345, while CD and CD 3 groups are giving positive signals CD 2 groups give negative signals. When the experiment is performed for angles of 210 or 330, positive signals are only observed for

8 346 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups Fig. 3. Simulated 2D 2 H MAXY-JRES NMR spectrum of the CD 2 CD group for θ = 195. Table 9. Real relative signal intensities of the 2D MAXY- JRES NMR experiment of CD n groups for several pulse angles θ. Spin θ = 195 θ = 210 θ = 225 θ = 270 system or 345 or 330 or 315 IS(CD) IS 2 (CD 2 ) IS 3 (CD 3 ) CD groups. For the angle of 270, all groups, CD, CD 2 and CD 3, give positive signals with the real relative signal intensities of 1, 6 and 27, respectively. When the pulse angle is 225 or 315, real relative signal intensities of the CD, CD 2 and CD 3 groups are 0.707, and 2.121, respectively. By comparing their real relative signal intensities obtained for the angles of 195, 210 and 270, one can easily distinguish CD, CD 2 and CD 3 groups from each other. After these identifications, the splitting of signals in the spectra of the 2D MAXY-JRES NMR experiment can be used for the identification of neighbour 2 H nuclei. The explanation forthisisgivenasfollows. For product operator description and spectrum simulation of multiple-pulse NMR experiments, a computer program was written by Kanters et al. [37, 38]. This is called Product Operator Formalism using Maple (POF.M). In order to obtain the simulated spectra, POF.M is implemented for Fourier transformation of our obtained theoretical results. In simulated spectra of CD n CD m groups, chemical shifts of 2 H nuclei are set to be 11, 7 and 3 ppm for CD, CD 2 and CD 3 groups, respectively. Spin-spin coupling constants between two 2 H nuclei are assumedtobe3,4and5hzincd 2 CD, CD 3 CD and CD 3 CD 2 groups, respectively. For the angle θ = 195, the simulated spectrum of the CD 2 CD group is presented in Fig. 3; three negative signals ( 1: 1: 1) and five positive signals (1 : 2 : 3 : 2 : 1) for CD 2 and CD groups, respectively, can be observed. In Fig. 4, the simulated spectrum of the CD 3 CD group is given for θ = 210. For this angle, as expected, only the CD group gives seven positive signals with an intensity distribution of 1:3:6:7:6:3:1. For the

9 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups 347 Fig. 4. Simulated 2D 2 H MAXY-JRES NMR spectrum of the CD 3 CD group for θ = 210. CD 3 CD 2 group, the simulated spectrum for θ = 270 is presented in Figure 5. For this angle, both CD 3 (five signals with an intensity distribution of 1:2:3:2:1) and CD 2 (seven signals with intensities of 1 : 3 : 6 : 7 : 6 : 3 : 1) groups give maximum positive signals. 5. Conclusion The 2D MAXY-JRES NMR experiment is a combination of MAXY and homonuclear J-resolved NMR spectroscopy. This technique is used for the identification of CH n CH m groups in complex samples. In this study, first, evolutions of some product operators under the homonuclear scalar spin-spin coupling Hamiltonian for an SS (S = 1, S = 1) spin system are obtained. Then, by using the product operator theory, analytical descriptions of the 2D MAXY-JRES experiment for IS n I S m (I = I = 1 2 ; S = S = 1; n = 1,2,3; m = 1,2) multi-spin systems are presented. The obtained results for each CD n CD m group represent the FID signals of this experiment. By using these results experimental suggestions are made and simulated spectra are obtained for various CD n CD m groups. As a result, it is shown that the 2D MAXY-JRES NMR experiment can be used to distinguish CD, CD 2 and CD 3 groups from each other in CD n CD m systems. Appendix A: Complete Product Operator Theory for the IS (I =1/2,S = 1) Spin System The complete product operator for the IS (I = 1/2, S = 1) spin system is presented in our previous study [36]. For this spin system, evolutions of nine angular momentum operators of spin S = 1 under r. f. pulse and chemical shift Hamiltonians were obtained, and they are given in Tables 2 and 3, respectively. For the IS (I = 1/2, S = 1) spin system evolutions of 32 product operators under the spin-spin coupling Hamiltonian are given in Table 4. The rest 8 product operators of E, I z, I z S z, S z, S 2 z, I zs 2 z, I x[s x,s y ] + and I y [S x,s y ] + do not change under the spin-spin coupling Hamiltonian.

10 348 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups Fig. 5. Simulated 2D 2 H MAXY-JRES NMR spectrum of the CD 3 CD 2 group for θ = 270. Appendix B: Product Operator Description of the 2D MAXY-JRES NMR Experiment for the IS 2 I S Multi-Spin System For the IS 2 I S multi-spin system, the density matrix at thermal equilibrium is σ 0 = S 1z + S 2z + S z.byusing the computer program the following density matrices for each labelled point are obtained: σ 0 90 x(s 1,S 2,S ) S 1y S 2y S y σ 1, (B1) σ 16 = 1 2 ( 2A + B + 2C D)c Ss θ ( 2C + D)c 2Jc S s θ (B D)c Sc 2θ s θ Dc 2Jc S c 2θ s θ D (c 2J c 4J c S c 2S s θ + c 2J c 4J c S c 2S c 2θ s θ ) (B D )(c S c 2S c 2θ s θ + c 4J c S c 2S c 2θ s θ (H 1J +H 2J ) ( =1/(2J IS ))+H J ( =1/(2J σ I S )) 1 2I z S 1x + 2I z S 2x + 2I z S x, (B2) 180 σ x(s 1,S 2,S )+90 x(i,i ) 2 2I y S 1x 2I y S 2x 2I y S x, (B3) (H 1J +H 2J ) ( =1/(2J IS ))+H J ( =1/(2J σ I S )) 3 2I x S 1xz + 2I x S 2xz + 2I xs xz, (B4) σ 4 90 x(s 1,S 2,S ) 2I x S 1xy 2I x S 2xy 2I xs xy σ 5, (B5) + c S c 2S s θ + c 4J c S c 2S s θ ) D s 2J s 4J c S c 2S c θ s 2θ +( F + G H)c Ss θ (G + H)c 2J c s s θ Hc 2 2J c S s θ, where A = S 1y + S 2y, B = S 1y (S2x 2 + S2y)+(S 2 1x 2 + S1y)S 2 2y, B = S 1y (S2x 2 S2y)+(S 2 1x 2 S1y)S 2 2y, (B6) (B7) (B8) (B9)

11 İ. Şaka and A. Gençten 2D MAXY-JRES NMR Spectroscopy of CD n CD m Groups 349 C = S 1y S 2 z + S 2yS 2 z, (B10) D = S 1y (S 2 2xS 2 z +S 2 2yS 2 z )+(S 2 1x +S 2 1y)S 2y S 2 z, (B11) D = S 1y (S 2 2xS 2 z S 2 2yS 2 z )+(S 2 1x S 2 1y)S 2y S 2 z, (B12) F = S y, G = S 2 1z S y + S2 2z S y, H = S 2 1z S2 2z S y. (B13) (B14) (B15) Also in (B1) (B6), H 1J = 2πJI z S 1z, H 2J = 2πJI z S 2z, and H J = 2πJI z S z. In the density matrix operator, only the terms with observable product operators are kept, as they are the only ones that contribute to the signal on y-axis detection. Then the magnetization along the y-axis is proportional to S 1y + S 2y + S y and M y (t 1,t 2 ) S 1y + S 2y + S y = Tr[(S 1y + S 2y )σ 16 ]+Tr[S yσ 16 ]. (B16) Now it is necessary to obtain the Tr[(S 1y + S 2y )O] and Tr[S y O ] values of the observable product operators indicated by O and O. These trace values are calculated by a computer program in Mathematica, and the results for several multi-spin systems are given in Tables 5 and 6. For example, the trace value of the S 1y + S 2y product operator for the IS 2 I S multi-spin system is calculated as 2 i=1 Tr[S iy O]=Tr[S 1y S 1y ]+Tr[S 2y S 2y ] = Tr[(E I S 1y E 2S E I E s) (E I S 1y E 2S E I E s)] + Tr[(E I E 1S S 2y E I E s ) = 144. By using Tables 5 and 6, (E I E 1S S 2y E I E s ) S 1y + S 2y + S y = 16(1 + 2c 2J )c S (1 2c 2θ )s θ 8(1 + 2c 2J ) 2 c S s θ (B17) (B18) is obtained for the IS 2 I S multi-spin system. This equation represents the FID signals of the 2D MAXY-JRES NMR experiment for the IS 2 I S multi-spin system. There exists triplet signals at (2J,Ω S ) : (Ω S) : ( 2J,Ω S ) coordinates with the intensity distribution of 1 : 1 : 1 for the S spin and five signals at (4J,Ω S ) : (2J,Ω S ) : (Ω S ) : ( 2J,Ω S ) : ( 4J,Ω S ) coordinates with the intensity distribution of 1:2:3:2:1fortheS spin. [1] M. Liu, R. D. Farrant, J. K. Nicholson, and J. C. Lindon, J. Magn. Reson. Series B 106, 270 (1995). [2] M. Liu, R. D. Farrant, J. K. Nicholson, and J. C. Lindon, J. Magn. Reson. Series A 112, 208 (1995). [3] M.Liu,R.D.Farrant,B.C.Sweatman,J.K.Nicholson, and J. C. Lindon, J. Magn. Reson. Series A 113, 251 (1995). [4] M. Liu, R. D. Farrant, J. K. Nicholson, and J. C. Lindon, Magn. Reson. Chem. 33, 212 (1995). [5] M. Liu, J. K. Nicholson, J. C. Lindon, P. N. Sanderson, and G. E. Tranter, Magn. Reson. Chem. 34, 865 (1996). [6] M.Liu,X.A.Moa,C.H.Ye,J.K.Nicholson,andJ.C. Lindon, J. Magn. Reson. 129, 67 (1997). [7] M. Liu, R. D. Farrant, J. K. Nicholson, and J. C. Lindon, Mol. Phys. 99, 1701 (2001). [8] D. M. Doddrell, D. T. Pegg, and M. R. Bendall, J. Magn. Reson. 48, 323 (1982). [9] H. Bildsøe, S. Dønstrup, H. J. Jakobsen, and O. W. Sørensen, J. Magn. Reson. 53, 154 (1983). [10] M. Liu and J. C. Lindon, Curr. Org. Chem. 5, 351 (2001). [11] K. H. Gardner and L. H. Kay, Annu. Rev. Biophys. Biomol. Struct. 27, 357 (1998). [12] O. W. Sørensen, G. W. Eich, M. H. Levitt, G. Bodenhausen, and R. R. Ernst, Prog. NMR Spectrosc. 16, 163 (1983). [13] F. J. M. Van De Ven and W. C. Hilbers, J. Magn. Reson. 54, 512 (1983). [14] K. J. Packer and K. M. Wright, Mol. Phys. 50, 797 (1983). [15] J. Shriver, Concepts Magn. Reson. 4, 1 (1992). [16] N. Chandrakumar and S. Subramanian, Modern Techniques in High Resolution FT NMR, Springer, New York, USA [17] N. Chandrakumar, J. Magn. Reson. 60, 28 (1984). [18] R. R. Ernst, G. Bodenhausen, and A. Wokaun, Principles of Nuclear Magnetic Resonance in One and Two Dimensions, Clarendon Press, Oxford [19] A. Gençten and F. Köksal, Spectrosc. Lett. 30, 71 (1997). [20] A. Gençten and Ö. Tezel, Spectrosc. Lett. 34, 317 (2001).

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