ESCA, Solid-State NMR, and X-Ray Diffraction Studies of

Publication Date (Web): July 4, 1996 ... and complexes of 1,8-bis(dimethylamino)naphthalene (DMAN) with HBF4, 1,2-dichloromaleic acid, and HNCS...
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J. Phys. Chem. 1996, 100, 11408-11419

ESCA, Solid-State NMR, and X-Ray Diffraction Studies of Perisubstituted Naphthalene Derivatives Krzysztof Wozniak,†,‡ Heyong He,‡ Jacek Klinowski,*,‡ Tery L. Barr,§ and Steven E. Hardcastle| Department of Chemistry, UniVersity of Warsaw, ul. Pasteura 1, 02-093 Warszawa, Poland, Department of Chemistry, UniVersity of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K., Department of Materials, Laboratory for Surface Studies, UniVersity of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, and AdVanced Analytical Facility, UniVersity of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201 ReceiVed: April 4, 1996X

We correlate ESCA, NMR, and X-ray diffraction measurements for 1,8-dinitro-2,7-dimethoxynaphthalene (DNMN), 1,8-diaminonaphthalene (DAN), 1,8-bis(4-toluenesulfonamido)naphthalene (PSAN), 1,8-bis(dimethylamino)-4-nitronaphthalene (NDMAN), 4-picryl-1,8-bis(dimethylamino)naphthalene (PDMAN), and complexes of 1,8-bis(dimethylamino)naphthalene (DMAN) with HBF4, 1,2-dichloromaleic acid, and HNCS. The strong ionic [N-H‚‚‚N]+ hydrogen bonds influence the binding energies of the core electrons of the donor and acceptor atoms. The substituent effect of the NO2 groups in DNMN increases the ipso angle at C(1) and C(8) and shortens the C(1)-C(2) bonds. In PDMAN, the electron-releasing substituent effect of the -NMe2 groups results in the shortening of the C-N bonds. The geometry of the N-H‚‚‚N bond in PSAN affects the C-N bond lengths and ipso angles. We assign the 1H and 13C NMR resonances in all compounds, the latter by examining the dipolar-dephased and short-contact-time spectra. There are welldefined trends in the chemical shifts of the nuclei at the different sites, and we rationalize their dependence on the density of valence electrons. In DMANH+BF4-, DMANH+ClMH-, and DMANH+NCS- the N(1s) ESCA peaks from the donor and acceptor atoms are shifted toward higher binding energies. We propose the difference between the binding energies of the donor and the acceptor as a measure of the strength and asymmetry of strong hydrogen bonds.

Introduction Electron spectroscopy for chemical analysis (ESCA), a direct method for the measurement of the electronic structure of molecules, is widely used in practical surface analysis.1-3 A photon of energy hν ejects an electron from an electronic bound state, and the kinetic energy (KE) of the ejected electron is measured. The binding energy, BE, the minimum energy required to remove an electron from a bound state in a molecule, is given by

BE ) hν - KE - Φ where Φ is the spectrometer work function. Low-energy photons (hν < 30 eV) eject electrons from the valence shell, while high-energy photons eject electrons from the atomic core levels. The characteristic features of the ionization band are the energy, width, shape, and relative intensity of the spectral peaks. Each of these parameters is sensitive to the electronic structure of the molecule from which the electrons originate. We correlate ESCA, solid-state NMR, and X-ray diffraction measurements for N,N-perisubstituted naphthalenes: 1,8-dinitro2,7-dimethoxynaphthalene (DNMN), 1,8-diaminonaphthalene (DAN), 1,8-bis(4-toluenesulfonamido)naphthalene (PSAN), 1,8bis(dimethylamino)-4-nitronaphthalene (NDMAN), 4-picryl-1,8bis(dimethylamino)naphthalene (PDMAN), and complexes of the aromatic diamine 1,8-bis(dimethylamino)naphthalene (DMAN) with tetrafluoroboric acid (DMANH+BF4-), with 1,2-dichloromaleic acid (DMANH+ClMH-), and with HNCS (DMANH+NCS-). The atom-numbering schemes are shown †

University of Warsaw. University of Cambridge. § Laboratory for Surface Studies, University of Wisconsin-Milwaukee. | Advanced Analytical Facility, University of Wisconsin-Milwaukee. X Abstract published in AdVance ACS Abstracts, June 15, 1996. ‡

S0022-3654(96)01029-5 CCC: $12.00

in Figure 1. The above compounds have different properties (basicity, electronegativity, substituent effect, size of substituents) that bring about structural and spectroscopic differences. The series consists of diamines, N,N-dimethyldiamines (proton sponges), their complexes with acids, and perinitro derivatives of naphthalene. Proton sponges4,5 have very high proton affinities or basicities and with mineral or organic acids form very stable ionic complexes containing intramolecular [N‚‚‚H‚‚‚N]+ hydrogen bonds. These model compounds have attracted considerable interest, giving rise to over 100 theoretical and experimental studies. The DMAN molecule and its complexes have been intensively studied in the solid state by means of X-ray diffraction,6,7 solid-state NMR,7-10 NQR7,11,12 at room and low temperatures, and ab-initio computational methods.13 The X-ray and spectroscopic data for DAN can be found in refs 14 and 15, for DMANH+BF4- in refs 9 and 16, for DMANH+NCS- in refs 9 and 17, and for DMANH+ClMHin ref 18. One can expect the variability of the N‚‚‚N distances in perisubstituted derivatives of naphthalene to influence significantly the ESCA spectra of these compounds. The changes in hydrogen bonding (weak N-H‚‚‚N bonds in the free amines versus strong cationic [N-H‚‚‚N]+ bonds in the complexes) should be helpful in assessing the effect of hydrogen bonding on the binding energies of core electrons of atoms in the molecules involved. Experimental Section X-ray Diffraction. Crystals of DNMN, PSAN, and PDMAN suitable for X-ray work were crystallized from acetonitrile by slow evaporation. X-ray measurements were made on an EnrafNonius CAD 4 diffractometer using monochromated Mo KR radiation and the ω-2θ scan mode. Three standard reflections were monitored per every 100 reflections collected and showed no significant decrease in standard intensity during © 1996 American Chemical Society

Perisubstituted Naphthalene Derivatives

J. Phys. Chem., Vol. 100, No. 27, 1996 11409

Figure 1. (a) Schematic representation and (b) atomic displacement parameters for perisubstituted naphthalenes. The ellipsoids have been drawn at the 50% probability level.

the data collection time. The data were corrected for the Lorentz and polarization effects, and the structure was solved by direct methods19 and refined using SHELXL-93.20 The refinement was based on F2 for all reflections except those with very negative F2. Weighted R factors ωR and all goodnesses-of-fit S values are based on F2. Conventional R factors are based on F with F set to zero for negative F2. The criterion Fo2 > 2σ(Fo2) was used only for calculating the R factors and is not relevant to the choice of reflections for refinement. R factors based on F2 are about twice as large as those based on F, and the R factors based on all data are even larger. Scattering factors and absorption coefficients were taken from Tables 6.1.1.4 and 4.2.4.2 in ref 21. Experimental details of data collection and

refinement are summarized in Table 1. All positional parameters are shown in Tables 2-4. We estimate the errors of the ipso angles at ca. 0.4° (compared with the average variation of this angle of at least 5°). The situation with the other angles is similar. The errors associated with N-C distances are in the 0.003-0.006 Å range (compared with the variation of this variable of ca. 0.1 Å). In all cases the errors associated with structural and spectroscopic variables are far smaller than the variation of a given variable for the entire series of compounds under consideration. Anisotropic thermal parameters as well as the full geometry of the compounds investigated are deposited as supporting information. Solid-State NMR. 1H magic-angle-spinning (MAS) NMR

11410 J. Phys. Chem., Vol. 100, No. 27, 1996

Wozniak et al.

TABLE 1: Crystal Data and Structure Refinement Details identification code empirical formula formula weight color temperature [k] wavelength [å] crystal system space group a [Å] b [Å] c [Å] R [deg] β [deg] γ [deg] volume [Å3] Z density (calc) [Mg/m3] absorption coefficient [mm-1] F(000) crystal size [mm] θ range for data collection [deg] index ranges

DNMN C12H10N2O6 278.22 yellow 293(2) 0.71073 monoclinic C2/c 13.512(1) 12.426(1) 7.859(1) 113.7(1) 1207.9(2) 4 1.530 0.125 576 0.20 × 0.25 × 0.30 2.4 to 24 -20 e h e 18 0 e k e 18 0 e l e 12 974 900 0.0143

reflections collected independent reflections R (int) refinement method data/restraints/parameters goodness-of-fit ) Sa final R indices [I > 2σ(I)] R1, ωR2 R indices (all data) R1, ωR2 largest diff. peak/hole [e Å-3] a

896/0/112 1.064

PSAN C22H18N2O4S2 438.50 white 293(2) 0.71073 triclinic P1h 9.928(1) 10.737(1) 12.308(1) 104.04(1) 105.86(1) 104.98(1) 1147.8(2) 2 1.269 0.261 456 0.20 × 0.35 × 0.30 1.8 to 35 -11 e h e 11 -12 e k e 12 0 e l e 14 4234 4025 0.0176 full-matrix least-squares on F2 4021/0/377 1.072

PDMAN C20H19N5O6 425.40 black 293(2) 0.71073 monoclinic P21/n 13.788(1) 10.346(1) 13.953(1) 94.32(1) 1984.7(3) 4 1.424 0.108 888 0.30 × 0.35 × 0.20 2.4 to 23 -16 e h e 16 0 e k e 12 0 e l e 16 2715 2591 0.0556 2586/0/351 0.989

0.0384, 0.110

0.0436, 0.1068

0.0701, 0.1869

0.0645, 0.128 0.215/-0.168

0.0836, 0.1167 0.244/-0.254

0.1262, 0.2057 0.411/-0.469

S ) [∑ω(Fo2 - Fc2)2/(N - M)]1/2, where N is the number of reflections and M is the total number of parameters.

TABLE 2: Non-Hydrogen-Atom Coordinates (×104) and Equivalent Displacement Parameters (Å2 × 103); Hydrogen Atom Coordinates (×103) and Their Isotropic Displacement Parameters (Å2 × 103) for DNMN

TABLE 3: Non-Hydrogen Atom Coordinates (×104) and Equivalent Displacement Parameters (Å2 × 103) for PDMAN; Hydrogen Coordinates (×103) and Their Isotropic Displacement Parameters (Å2 × 103)

atom

x

y

z

U(eq/iso)

atom

x

y

z

U(eq/iso)

O(1) O(2) O(3) N(1) C(1) C(2) C(3) C(4) C(9) C(10) C(11) H(3) H(4) H(111) H(112) H(113)

4046(2) 3793(2) 2425(1) 3973(1) 4089(2) 3241(2) 3264(2) 4119(2) 5000 5000 1459(2) 268(2) 413(2) 98(2) 158(2) 115(2)

2075(1) 2063(2) 3673(1) 2526(2) 3693(2) 4262(2) 5396(2) 5902(2) 4194(2) 5343(2) 4216(3) 582(2) 665(2) 374(3) 467(3) 465(3)

4019(3) 1160(3) 2836(2) 2600(3) 2636(3) 2732(3) 2715(3) 2611(3) 2500 2500 2655(5) 282(3) 250(3) 268(4) 367(4) 150(4)

83(1) 84(1) 60(1) 50(1) 41(1) 47(1) 55(1) 54(1) 40(1) 45(1) 69(1) 63(7) 64(7) 93(10) 88(9) 97(10)

O(1) O(2) O(3) O(4) O(5) O(6) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) N(1) N(2) N(3) N(4) N(5) H(111) H(112) H(113) H(141) H(142) H(143) H(2) H(3) H(5) H(6) H(7) H(17) H(19) H(121) H(122) H(123) H(131) H(132) H(133)

9327(3) 9108(3) 10443(3) 9949(3) 6710(3) 7850(3) 6368(3) 6352(3) 7001(3) 7658(3) 8449(3) 8598(3) 8132(4) 7467(3) 7182(3) 7766(3) 5001(4) 5200(4) 7170(5) 7203(6) 8276(3) 8933(3) 9474(3) 9395(3) 8788(4) 8233(3) 5640(3) 7092(3) 9118(3) 9981(3) 7544(3) 544(4) 460(4) 439(6) 697(5) 667(6) 790(6) 587(4) 698(3) 879(3) 911(4) 830(3) 977(3) 873(3) 499(4) 452(5) 565(4) 716(5) 665(6) 777(9)

413(4) 2472(4) 3756(5) 2751(5) -482(4) -1125(5) -1738(5) -429(5) 275(5) -341(5) -2378(5) -3645(5) -4330(5) -3725(5) -2413(5) -1691(5) -1719(7) -3526(7) -3708(9) -5716(7) 443(4) 1356(5) 2167(5) 2058(5) 1180(5) 416(5) -2413(4) -4358(4) 1413(5) 2900(5) -483(4) -108(5) -239(5) -116(7) -619(6) -604(8) -607(7) 2(4) 1178(4) -187(5) -413(5) -531(5) 284(4) 116(4) -432(6) -339(5) -400(5) -264(7) -402(7) -404(10)

5886(2) 5820(3) 2782(3) 1488(3) 2695(3) 1839(3) 5667(3) 5632(3) 5128(3) 4605(3) 4165(3) 4285(3) 4982(4) 5528(3) 5294(3) 4665(3) 6694(5) 5619(5) 7221(4) 6372(7) 4003(3) 4408(3) 3895(4) 2912(3) 2442(4) 3001(3) 6084(3) 6290(3) 5468(3) 2355(4) 2477(3) 716(4) 692(4) 631(5) 567(5) 673(6) 654(5) 585(3) 515(3) 381(4) 393(4) 511(3) 417(3) 179(4) 605(4) 542(4) 523(4) 721(5) 748(6) 764(9)

58(1) 67(1) 87(2) 92(2) 68(1) 75(1) 37(1) 44(1) 42(1) 38(1) 39(1) 45(1) 48(1) 40(1) 34(1) 37(1) 64(2) 60(2) 69(2) 82(2) 38(1) 39(1) 44(1) 44(1) 49(1) 43(1) 45(1) 54(1) 43(1) 62(1) 52(1) 54(14) 58(15) 115(24) 80(20) 115(26) 103(22) 39(12) 23(11) 41(14) 63(15) 35(11) 26(10) 31(11) 68(16) 61(16) 43(13) 94(22) 104(25) 197(45)

spectra and 13C spectra with MAS and 1H-13C cross-polarization (CP/MAS) were recorded at room temperature and 123 K at 399.9 and 100.6 MHz, respectively, using a Chemagnetics CMX-400 spectrometer. Zirconia rotors were spun in nitrogen gas at different rates in order to identify sidebands and resonance overlaps. 1H spectra were measured with spinning at 9-12 kHz using 2 µs (30°) pulses and 3 s recycle delays. Single contact 1H-13C CP/MAS experiments were performed with 4 ms contact times and short-contact-time experiments with 50 µs contact times. The 1H π/2 pulses were typically 2.5 µs, the recycle delay 5 s, and the MAS rate 5-9 kHz. Dipolardephased 1H-13C spectra were recorded with a 50 µs delay prior to acquisition, 4 ms contact time, and 5 s recycle delays. Conventional MAS spectra contain resonances from all carbons, dipolar-dephased spectra identify resonances from the quaternary carbons, and short-contact-time CP spectra reveal the protonated carbons. We estimate the error of the solid-state NMR chemical shifts at, at most, 0.5 ppm, far smaller than the (ca. 15-24 ppm) range of chemical shift variation for the series of compounds considered in this work.

Perisubstituted Naphthalene Derivatives

J. Phys. Chem., Vol. 100, No. 27, 1996 11411

TABLE 4: Non-Hydrogen Atom Coordinates (×104) and Equivalent Displacement Parameters (Å2 × 103) for PDMAN; Hydrogen Coordinates (×103) and Isotropic Displacement Parameters (Å2 × 103) atom S(1) S(2) O(1) O(2) O(3) O(4) N(1) N(2) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) H(2) H(3) H(4) H(5) H(6) H(7) H(12) H(13) H(15) H(16) H(18) H(19) H(21) H(22) H(1n) H(2n) H(231) H(232) H(233) H(241) H(242) H(243)

x 76(1) 2163(1) 548(3) -1178(2) 2612(3) 2539(2) -251(3) 313(3) -788(3) 1189(4) -1827(4) -2070(4) -1882(4) -1479(4) -768(4) -487(3) -952(3) -1649(3) 1593(3) 2914(4) 4113(4) 4035(4) 2710(4) 1498(4) 2763(3) 3063(4) 3475(4) 3609(4) 3351(4) 2931(4) 5332(5) 4007(6) -102(4) -208(4) -244(4) -236(4) -176(5) -44(4) 300(3) 498(4) 267(4) 57(4) 300(4) 359(40) 345(4) 279(4) 4(4) 6(3) 620(4) 554(4) 500(4) 417(5) 335(5) 491(5)

y 2255(1) 6877(1) 2488(2) 1060(2) 6432(2) 6431(2) 3628(3) 6271(2) 3933(3) 3000(4) 3257(4) 4436(4) 6713(4) 7719(4) 7547(3) 6362(3) 5248(3) 5461(3) 2212(3) 3325(3) 3258(3) 2119(3) 1020(4) 1045(3) 8672(3) 9369(4) 10773(4) 11503(4) 10782(4) 9377(4) 2090(6) 13027(4) 219(4) 257(4) 465(3) 677(4) 836(5) 818(4) 408(3) 389(4) 22(4) 34(3) 891(4) 1116(4) 1123(4) 889(4) 426(3) 662(3) 229(3) 272(4) 159(4) 1335(4) 1325(4) 1352(4)

z 2791(1) 4455(1) 4053(2) 1996(2) 5450(2) 3427(2) 2674(2) 3964(2) 1628(2) 520(3) -525(3) -461(3) 704(4) 1756(4) 2825(4) 2833(3) 1740(2) 655(3) 2326(2) 2849(3) 2508(3) 1654(3) 1153(3) 1491(3) 4970(3) 6149(3) 6534(4) 5757(4) 4598(4) 4187(3) 1255(5) 6178(7) 50(3) -128(4) -111(3) -3(3) 170(4) 360(3) 344(3) 291(3) 59(3) 114(3) 664(3) 726(3) 407(3) 336(3) 335(3) 453(3) 184(3) 77(3) 51(3) 560(4) 633(3) 680(4)

U(eq/iso) 41(1) 49(1) 52(1) 52(1) 77(1) 63(1) 41(1) 41(1) 38(1) 51(1) 62(1) 62(1) 63(1) 63(1) 52(1) 38(1) 37(1) 48(1) 39(1) 49(1) 54(1) 49(1) 58(1) 50(1) 45(1) 58(1) 70(1) 63(1) 65(1) 58(1) 81(1) 97(2) 68(10) 81(13) 65(10) 57(11) 108(16) 65(11) 50(9) 58(11) 61(10) 55(10) 69(13) 63(11) 78(12) 70(10) 55(10) 41(9) 112(9) 146(11) 129(10) 187(16) 145(12) 131(13)

TABLE 5: Selected Geometrical Parameters: Bond Lengths [Å] and Angles [deg] for Perisubstituted Naphthalenesa parameter N(1)-C(1) N(2)-C(8) C(1)-C(2) C(1)-C(9) C(2)-C(3) C(3)-C(4) C(4)-C(10) C(5)-C(6) C(5)-C(10) C(6)-C(7) C(7)-C(8) C(8)-C(9) C(9)-C(10) N(1)...N(2)

DNMN 1.458(3)

N(1)-C(1)-C(9) N(1)-C(1)-C(2) C(2)-C(1)-C(9) C(1)-C(2)-C(3) C(2)-C(3)-C(4) C(3)-C(4)-C(10) C(4)-C(10)-C(9) C(5)-C(10)-C(9) C(4)-C(10)-C(5) C(10)-C(5)-C(6) C(5)-C(6)-C(7) C(6)-C(7)-C(8) C(7)-C(8)-C(9) C(7)-C(8)-N(2) C(9)-C(8)-N(2) C(8)-C(9)-C(10) C(8)-C(9)-C(1)

121.6(2) 115.2(2) 123.1(2) 119.4(2) 119.3(2) 122.7(2) 119.5(1)

Results and Discussion X-ray Analysis. 1,8-Dinitro-2,7-dimethoxynaphthalene (DNMN) crystallizes in the monoclinic C2/c space group with four molecules in the unit cell (Table 1). The labeling schemes of all molecules and the ORTEP representation of thermal motions of atoms in new structures described in this work are shown in parts a and b of Figure 1, respectively. Selected structural parameters are given in Table 5. The plane of the

1.428(4) 2.841(3)

121.0(3)

128.1(2)

PDMAN 1.388(6) 1.382(6) 1.355(7) 1.451(6) 1.386(7) 1.363(6) 1.407(6) 1.335(7) 1.405(6) 1.398(7) 1.385(7) 1.444(6) 1.444(6) 2.838(6)

118.8(3) 121.3(3) 119.9(3) 121.6(3) 120.4(3) 121.0(3) 120.0(3) 119.8(3) 120.2(3) 121.7(4) 119.6(4) 121.4(4) 120.8(3) 118.7(3) 120.5(2) 116.7(3) 126.4(3)

120.8(4) 120.5(4) 118.7(4) 122.2(5) 120.5(5) 120.2(4) 119.3(4) 117.7(4) 123.0(5) 122.5(5) 120.7(5) 120.7(5) 118.8(4) 120.8(5) 120.6(4) 118.0(4) 125.2(4)

a

Structural data for the other perisubstituted systems analazed are available in the Cambridge Structural Database41 and ref 18. The naphthalene labeling scheme has been applied for DNMN. The parameters not reported in the table are equal to the reported values by symmetry.

TABLE 6: Shortest Intermolecular Contacts Which May Be Considered as Weak C-H‚‚‚O Hydrogen Bonds D-H‚‚‚A C(3)-H(3)‚‚‚O(1) C(3)-H(3)‚‚‚O(2) C(11)-H(111)‚‚‚O(1) C(13)-H(132)‚‚‚O(1)

ESCA. ESCA spectra were recorded on a Hewlett-Packard (HP) 5950A spectrometer equipped with a high-resolution X-ray monochromator. A conventional Al KR anode was used as a source of radiation. The background pressure during analysis was ca. 1 × 10-9 Torr. The materials under study are insulators which produce distinctive charging shifts.22 These were removed and the binding scale was established using a combination of electron flood guns and fixing the C(1s) binding energy of the hydrocarbon part carbons at 284.6 eV. This procedure has been successfully applied before.2,23 A broad survey scan with the 0-1000 eV scan range was run to identify all elements. Detailed scans (20 eV wide), recorded to establish the precise peak location, were used for spectral deconvolution. The C(1s) line used for charge referencing was run at the beginning, in the middle, and at the end of the data collection, and its position was constant with time.

1.374(3) 1.421(2) 1.410(3) 1.346(3) 1.411(3)

PSAN 1.403(4) 1.442(4) 1.363(4) 1.441(4) 1.363(4) 1.337(3) 1.410(5) 1.349(6) 1.412(5) 1.373(4) 1.373(4) 1.431(4) 1.428(4) 2.720(4)

C(14)-H(143)‚‚‚O(2) C(7)-H(7)‚‚‚O(2) C(11)-H(111)‚‚‚O(3) C(11)-H(112)‚‚‚O(6) C(11)-H(113)‚‚‚O(5) C(13)-H(133)‚‚‚O(3) C(2)-H(2)‚‚‚O(4) C(6)-H(6)‚‚‚O(5) N(1)-H(1n)‚‚‚N(2) N(2)-H(2n)‚‚‚O(1) C(6)-H(6)‚‚‚O(2) C(18)-H(18)‚‚‚O(2) C(15)-H(15)‚‚‚O(2) C(13)-H(13)‚‚‚O(3) C(24)-H(243)‚‚‚O(4)

symmetry DNMN (0.5- X, 0.5+Y, 0.5-Z) (0.5-X, 0.5+Y, 0.5-Z) (0.5-X, 0.5-Y, 1-Z) PDMAN (1.5-X, -0.5+Y, 1.5-Z) (X, -1+Y, Z) (X, -1+Y, Z) (-0.5+X, 0.5-Y, 0.5+Z) (-0.5+X, -0.5-Y, 0.5+Z) (1-X, -Y, 1-Z) (2-X, -Y, 1-Z) (-0.5+X, 0.5-Y, 0.5+Z) (0.5-X, 0.5+Y, 0.5-Z) PSAN (-X, 1-Y, 1-Z) (X, 1+Y, Z) (-X, 1-Y, 1-Z) (-X, -Y, -Z) (1-X, 1-Y, 1-Z) (1-X, 2-Y, 1-Z)

DD-H H‚‚‚A D‚‚‚A H‚‚‚A [Å] [Å] [Å] [deg] 0.98

2.69

3.539

145

0.98

2.87

3.844

169

0.88

2.80

3.363

123

0.89

2.90

3.590

150

1.04 1.05 1.08

2.51 2.70 2.55

3.362 3.726 3.454

139 164 141

1.08

2.85

3.729

152

1.13 1.03 0.89

2.73 2.60 2.80

3.432 3.292 3.632

120 124 155

1.02

2.83

3.355

113

0.85 0.84 0.82 0.87 0.95 0.87 0.92

2.03 2.09 2.71 2.78 2.91 2.83 2.62

2.720 2.935 3.453 3.365 3.626 3.401 3.203

138 179 151 126 134 125 122

nitro groups is almost perpendicular to the plane of the naphthalene ring, with O(2)-N(1)-C(1)-C(2) and O(1)N(1)-C(1)-C(9) angles of 107.4(2)° and 111.2(2)°, respectively. The methoxy group is in the trans position with respect to the -NO2 group, which is characteristic of 1,2,7,8-foursubstituted naphthalenes. The DNMN molecules are stacked along the Z axis and form a nice 2D pattern in the XY plane (Figure 2). The columns of molecules are arranged in such a manner that the -NO2 groups in a molecule in the stack (positions 1 and 8) have above and below hydrogens in positions

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Figure 2. Packing of the DNMN molecules in the crystal lattice: (a) XY projection; (b) YZ projection.

Figure 3. Geometry of weak attractive N‚‚‚O interactions: (a) intramolecular N‚‚‚O interactions in DNMN; (b) intermolecular N‚‚‚O interactions in PDMAN.

TABLE 7: Geometry of Weak N‚‚‚O Contacts between Different Nitro Groups in DNMN and PDMANa N‚‚‚O contact: C-NO(1)O(2)‚‚‚O(a) symmetry operator a N‚‚‚O(a) [Å] O(a)‚‚‚N-O(1) [deg] O(a)‚‚‚N-O(2) [deg] O(a)‚‚‚N-C [deg] O(a)‚‚‚O(1) [Å] O(a)‚‚‚O(2) [Å] O(a)‚‚‚C [Å] O(1)‚‚‚C(1) [Å] O(1)‚‚‚O(2) [Å] O(2)‚‚‚C(1) [Å]

DNMN C(1)-N(1)O(1)O(2)‚‚‚O(2a) 1-X, Y, 0.5-Z N(1)‚‚‚O(2) ) 2.832 O(2a)‚‚‚N(1)O(1) ) 84.8 O(2a)‚‚‚N(1)O(2) ) 90.6 O(2a)‚‚‚N(1)C(1) ) 96.0 O(2a)‚‚‚O(1) ) 2.979 O(2a)‚‚‚O(2) ) 3.089 O(2a)‚‚‚C(1) ) 3.317 O(1)‚‚‚C(1) ) 2.298 O(1)‚‚‚O(2) ) 2.132 O(2)‚‚‚C(1) ) 2.888

PDMAN C(18)-N(4)O(3)O(4)‚‚‚O(5a) 1.5-X, 0.5+Y, 0.5-Z N(4)‚‚‚O(5) ) 2.867 O(5)‚‚‚N(4)O(3) ) 88.9 O(5)‚‚‚N(4)O(4) ) 94.6 O(5)‚‚‚N(4)C(18) ) 83.1 O(5)‚‚‚O(3) ) 3.095 O(5)‚‚‚O(4) ) 3.204 O(5)‚‚‚C(18) ) 3.054 O(3)‚‚‚C(18) ) 2.290 O(3)‚‚‚O(4) ) 2.150 O(4)‚‚‚C(18) ) 2.294

a Symbol O(2a) labels the O(2) atom from a molecule related by symmetry operator a (1-X, Y, 0.5-Z for DNMN and 1.5-X, 0.5+Y, 0.5-Z for PDMAN).

4 and 5 and vice versa. Since the DNMN molecule has a dipole moment, such an arrangement suggests that the driving force of ordering is weak intermolecular dipole-dipole interactions, while the ordering in the XY plane seems to be due to weak intermolecular C-H‚‚‚O interactions between the methoxy C-H bond and oxygens from the nitro groups. The geometry of these weak intermolecular contacts is given in Table 6. The presence of relatively short -NO2‚‚‚O contacts also suggests the presence of weak attractive intramolecular N‚‚‚O interactions.24-26 The geometry of this contact is given in Table

7 and Figure 3. Table 7 contains all the parameters that we believe should be reported when attractive N‚‚‚O interactions between a nitro group and an oxygen atom are discussed. Those parameters can be considered as a standard for the N‚‚‚O interactions, just as the D-H, H‚‚‚A, D‚‚‚A, and D-H‚‚‚A parameters (where D and A stand for donor and acceptor) are standard for hydrogen bonding. The geometry of DNMN is the result of an interplay between the electron-withdrawing influence of the nitro groups, conjugation between electron densities of these groups and the methoxy groups, and weak through-space interactions between the nitro groups (assisted by the rotation of the nitro groups around the C(1)-N(1) and C(8)-N(2) bonds). As a result of the substituent effect of the NO2 groups, the ipso angle at C(1) and C(8) increases to 123.1(2)o and the C(1)-C(2) bonds shorten to 1.374(3) Å. PDMAN. 4-Picryl-1,8-bis(dimethylamino)naphthalene (PDMAN) crystallizes in the monoclinic P21/n space group with one molecule in the general position in the independent part of the unit cell. The labeling of atoms and the thermal parameters are shown in Figure 1. PDMAN was prepared by the addition of an equimolar amount of picryl chloride and DMAN in acetonitrile.27 It has been postulated on the basis of NMR spectra27 that picryl chloride, as well as 4,6-dinitrobenzofuroxan

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Figure 4. (a) 3D arrangement of PDMAN molecules; (b) packing of PSAN molecules.

Figure 5. (a) N‚‚‚N interatomic distances versus N-C bond lengths (R ) -0.94 for 7 data points); (b) correlation between N-C bond lengths and average ipso angles (R ) 0.89 for 8 data points); (1) DNMN, (2) DAN, (3) PSAN, (4) PDMAN, (5) DMANH+BF4-, (6) DMANH+ClMH-, (7) DMANH+SCN-, (8) DMAN. The dashed lines in Figure 5b define the confidence interval for the slope. Interatomic distances and bond lengths are in angstroms, and bond angles in degrees.

and furazan, a very strong aromatic electrophile, forms with DMAN C-bonded adducts. However, we have obtained PDMAN. Despite the asymmetric substitution, there are no significant differences in the geometries of the two halves of the PDMAN moiety. This is due to the relatively high esd’s of the structural parameters. The 1,8-bis(dimethylamino)naphthalene fragment of PDMAN is similar to DMAN itself.6,7 The electron-releasing substituent effect of the -NMe2 groups results in the shortening

of the C-N bonds. The picryl part of PDMAN is almost perpendicular (at the angle of 69.1°) to the naphthalene plane. As a result of the superposition of substituent effects of the nitro groups and the naphthalene part of PDMAN, the angles in the picryl fragment alternate in the 113.3-124.6° range. The 3D arrangement of PDMAN molecules (Figure 4a) shows short intermolecular contacts between oxygens and the -NO2 groups from neighboring molecules (Table 7). The -NO2 groups are also involved in weak C-H‚‚‚O hydrogen bonds (Table 6). PSAN. 1,8-Bis(4-toluenesulfonamido)naphthalene (PSAN) crystallizes in the triclinic P1h space group with two molecules in the unit cell. The molecules adopt an asymmetric conformation with the paramethylphenylsulfo groups shifted apart. The atom-labeling scheme and the illustration of thermal motion parameters are defined in Figure 1, and the packing of the molecules in the crystal lattice is shown in Figure 4b. The most characteristic feature of this structure is the weak N-H‚‚‚N hydrogen bond formed between N(1)-H(1n) and N(2) atoms. The geometry of this bond [N(1)‚‚‚N(2) ) 2.720(4) Å, H(1n)‚‚‚N(2) ) 2.03(4) Å, and N(1)H(1n)N(2) ) 138°] is very different from the geometry of the cationic [N-H‚‚‚N]+ hydrogen bond in proton sponges.26,28-38 The O(1) and O(4) oxygens, which are quite near the hydrogen bond site, must also influence this bond. The influence of the N-H‚‚‚N bond on the geometry of the aromatic part is seen in the magnitude

11414 J. Phys. Chem., Vol. 100, No. 27, 1996

Figure 6. 1H MAS NMR spectra of (a) DMAN, (b) DAN, (c) PSAN, (d) NDMAN, and (e) PDMAN.

of the C-N bond lengths and ipso angles (Table 5). There are other weak hydrogen bonds in this structure such as N(2)H(2n)‚‚‚O(1) (-X, 1-Y, 1-Z) and a number of weak C-H‚‚‚O bonds (Table 6). The main structural consequence of the change of substituents in peri positions is variation of the N‚‚‚N distances and N-C bond lengths (Figure 5a). The decrease of the N‚‚‚N distance is associated with the increase of the N-C bond lengths. The data points for the perinitro-derivative deviate significantly from those for the other derivatives. There is also a difference between DNMN and the other compounds in the series. The nitro groups in DNMN are very different from the other substituents in this series. The other compounds are essentialy amines, and this may be a reason for such a big discrepancy in the nitro data points (see Figure 5a). The nitro groups in DNMN interact via attractive N‚‚‚O interactions, while in the other compounds the main interaction between substituents is the repulsion between the lone electron pairs of the nitrogen atoms. This may be another explanation for the deviations in this compound. On the other hand, the changes of the C-N bonds are related to the changes of the ipso angles at the C(1) and C(8) atoms (Figure 5b). This is due to the substituent effects of 1,8 substituents and may be rationalized in terms of the Walsh-

Wozniak et al. Bent rule.39,40 A shift of electron density from the ipso carbon to a σ-electron-withdrawing substituent is best accomplished through an increase in the p-character of the hybrid sp2 orbital that points toward the substituent. As a consequence, the p-character of the other two hybrid sp2 orbitals is decreased, which results in an increase of the ipso R angle and a shortening of the bonds that form this angle. There are a number of other correlations and trends between structural parameters of the perisubstituted system. All reveal structural changes remote from the peri positions that are induced by variation of the substituents in these positions. All these structural changes are interrelated. Solid-State NMR. All 1H MAS NMR spectra shown in Figure 6 consist of broad peaks with two maxima, except for NDMAN, which gives a broad peak and a shoulder. The maxima with higher chemical shifts come from hydrogens attached to aromatic carbons, and the others from aliphatic hydrogens or hydrogens from the amino groups. Unlike in proton sponges,9,10,18,26 hydrogens involved in normal N-H‚‚‚N hydrogen bonds (as in DAN or PSAN) do not give large chemical shifts (up to ca. 20 ppm). The 13C resonances have been assigned by examining the dipolar-dephased and short-contact-time spectra and by reference to the literature.7-9 Previously unpublished 1H-13C CP/MAS, short-contact-time, and dipolar-dephased spectra of the aromatic regions of the molecules are shown in Figure 7. Spectra (a) contain peaks from all aromatic carbons in the complex, the short-contact-time spectra b show only resonances from protonated carbons, and the dipolar-dephased spectra c show only resonances from the quaternary carbons. In the case of DNMN there are four peaks from the quaternary carbons and two from the C-H carbons. We assign the peak at 153.2 ppm to C(1) and C(8) nuclei and the peak at 130.0 ppm to C(2) and C(7). Two less intense peaks at 122.0 and 116.4 ppm come from the C(10) and C(9) nuclei, respectively. The peak from C(3) in the short-contact-time spectrum has a lower chemical shift (110.2 ppm) than the peak from C(4) (133.8 ppm). In DAN the situation is far more complicated, because there are two molecules in the independent part of the unit cell14,15 which differ only slightly in the N-H‚‚‚N hydrogen bonds formed by the -NH2 groups in the peri positions. In any case, the resonances in the dipolar-dephased spectrum are unsplit, which means that in both spectra the lines from the quaternary carbons are superimposed. The peaks at 144.1, 135.9, and 115.9 ppm come from C(1) + C(8), C(10), and C(9) carbons, respectively. There are five peaks in the short-contacttime spectrum from 12 nuclei in the two independent molecules. The resonances from C(4) (at ca. 115 ppm) and C(2) (at ca. 110 ppm) are split and may come from two separate molecules, while C(3) and C(6) give resonances at 125.4 ppm. The 13C CP/MAS spectrum of PSAN consists of wellseparated peaks from C(1) (146.9 ppm), C(10) (137.9 ppm), C(9) (120.0 ppm), C(3) (128.6 ppm), C(4) (123.8 ppm), and C(2) (111.1 ppm). Most of the lines are superimposed with resonances from the phenyl part of PSAN. Given the strong asymmetry introduced by the -NO2 group at position 4 of the perisubstituted naphthalene ring, a unique spectral assignment must be proposed for NDMAN, which gives five lines in the dipolar-dephased spectrum. Thus, the lines at 157.0 and 151.4 ppm come from C(1) and C(8), respectively. The resonance at 114.2 ppm comes from C(9), and peaks at 133.7 and 129.7 ppm come from C(10) and C(4), respectively. The three peaks in the short-contact-time spectrum of NDMAN that appear at 126.9, 112.5, and 107.5 ppm are superimposed lines from C(3) and C(6) nuclei, C(5) [superimposed with one resonance from C(2) or C(7)], and C2 and C(7), respectively.

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Figure 7. Aromatic region of the 1H-13C CP/MAS NMR spectra of perisubstituted naphthalenes at room temperature: (a) CP/MAS spectra; (b) short-contact-time spectra; (c) dipolar-dephased spectra.

Figure 8. The most significant correlations between the average 13C chemical shifts: (a) [C(4) + C(5)]/2 versus [C(2) + C(7)]/2 (R ) 0.82 for 8 data points); (b) [C(2) + C(7)]/2 versus C(10) (R ) -0.80 for 7 data points); (1) DNMN; (2) DAN; (3) PSAN; (4) PDMAN; (5) DMANH+BF4-; (6) DMANH+ClMH-; (7) DMANH+SCN-; (8) DMAN.

Figure 9. The most significant correlations between the average 13C chemical shifts and the average structural parameters: (a) [C(4) + C(5)]/ 2 versus the average ipso angle (R ) 0.85 for 8 data points); (b) [C(4) + C(5)]/2 versus the average C(3)-C(4)-C(10) and C(10)-C(5)-C(6) angle (R ) 0.70 for 8 data points); (c) [C(4) + C(5)]/2 versus the average N-C bond length (R ) 0.79 for 8 data points); (d) C10 versus the average C(1)-C(2)-C(3) and C(6)-C(7)-C(8) angle (R ) 0.80 for 7 data points); (1) DNMN; (2) DAN; (3) PSAN; (4) PDMAN; (5) DMANH+BF4-; (6) DMANH+ClMH-; (7) DMANH+SCN-; (8) DMAN. Bond lengths and nonbonded distances are in angstroms, and angles in degrees.

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Figure 10. C(1s) ESCA spectra of (a) DNMN, (b) DAN, (c) PSAN, (d) NDMAN, (e) PDMAN, (f) DMANH+BF4-, (g) DMANH+ClMH-, and (h) DMANH+SCN-.

The spectrum of PDMAN is also relatively well resolved. We assign the intense line 153.1 ppm to C-NO2 carbons in the picryl group, and the lines from the C(1) and C(8) nuclei are at 146.9 ppm. The lines from C(9) and C(10) are in regions characteristic for these nuclei at 117.6 and 135.6 ppm. The short-contact-time spectrum contains an intense line from the C-H carbons of the picryl group at 112.8 ppm and lines from C(3) and C(6), C(4), and C(2) and C(7) at 127.2, 122.4, and 118.7 ppm, respectively. The complete peak assignment in the 13C MAS NMR spectra for all the compounds in the series is shown in Table 8. The most pronounced trends between the chemical shifts of the different nuclei are shown in Figure 8. First, the increase of the chemical shift of carbon at position 2 of the naphthalene fragment is associated with the increase of the chemical shift of carbon in position 4, so both these positions react to perturbation in the peri positions in a similar way. Second, the changes of chemical shifts of carbons at positions 10 and 2 have opposite signs. There is a number of similar but weaker correlations. Correlations between chemical shifts of different carbons map the redistribution of electron density upon a given structural perturbation. The variation of the density of the valence electrons in the series of naphthalenes also leads to changes in bond lengths

and angles. Correlations should therefore be observed between the chemical shifts and structural parameters. The most significant of such correlations, shown in Figure 9, indicate that the changes of the average N-C bond lengths are related to the change in the chemical shift, especially at position 4 (and to a lesser degree in other positions), which is in turn related to changes in the C(2)-C(1)-C(9) and C(3)-C(4)-C(10) angles. The variation of the chemical shift of carbon C(10) is correlated with changes of the C(3)-C(4)-C(10) angle. Results from a larger number of perisubstituted derivatives of naphthalene would enable us to make these correlations more quantitative. The dependence of the chemical shift on the density of valence electrons may be rationalized by analyzing the different contributions to the shielding constant.10,42,43 The chemical shift is defined as the difference between the shielding constants of a standard and the sample. On the other hand, the main contribution to the shielding constant comes from local paramagnetic shielding,44 which is a function of the electron density at the given atom: the lower the electron density, the larger the chemical shift. These changes are also related to changes in structural parameters. ESCA. The C(1s), O(1s), and N(1s) ESCA spectra of the perisubstituted naphthalenes, given as plots of the number of electrons in a small fixed energy interval versus electron binding

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J. Phys. Chem., Vol. 100, No. 27, 1996 11417

Figure 11. O(1s) ESCA spectra of (a) DNMN, (b) DAN, (c) PSAN, (d) NDMAN, (e) PDMAN, (f) DMANH+BF4-, (g) DMANH+ClMH-, and (h) DMANH+SCN-.

TABLE 8: Final Peak Assignment of the MAS NMR Spectraa atom C(1) C(2)

DNMN 153.2 130.0

C(3) C(4)

110.2 133.8

C(5) C(6) C(7)

DAN 144.1 111.9 109.6 125.4 118.9 114.5 118.9 114.5 125.4 111.9 109.6 144.1 115.9 135.9

PSAN 146.9 111.1

PDMAN 146.9 118.7

128.6 123.8

NDMAN 157.0 112.5 107.5 126.9 129.7

123.8

112.5

112.8

128.6 111.1

126.9 112.5 107.5 151.4 114.2 133.7 44.9 39.9 3.2

127.2 118.7

3.2

C(8) C(9) C(10) CH3

116.4 122.0 58.1

Haliph.

1.8

4.2

146.9 120.0 137.9 22.7 21.0 2.0

Harom.

2.6

6.1

6.6

127.2 122.4

146.9 117.6 135.6 46.1 41.5 1.1 1.7 2.8

Because of the symmetry, in DMANH+ClMH-, DMANH+NCS-, and DMAN the peaks from C(5), C(6), C(7), and C(8) overlap with the peaks from C(4), C(3), C(2), and C(1), respectively (refs 7-10 and 18). a

DMANH+BF4-,

energy, are shown in Figures 10-12. The C(1s) spectrum of DAN is quite different from the other spectra and contains several notable features. The presence of peaks at ca. 290.7 eV and shoulders at 288.5 eV suggests that the sample is contaminated by oxidation products. Similar small peaks in

the spectrum of DMANH+ClMH- come from carboxylic groups in the dichloromaleic anion.18 The O(1s) spectra are shown in Figure 11. The spectrum of DAN has a very complex structure resulting from the presence of the product of oxidation of 1,8-diaminonaphthalene. The line width is very sensitive to the peak being a composite. The details of the spectrum of the DMANH+ClMH- complex are discussed in ref 18. The most interesting ESCA spectra of perisubstituted naphthalenes are the N(1s) spectra shown in Figure 12. First, the N(1s) peaks from the nitro groups are markedly shifted toward higher binding energies. This is due to the electronegative oxygens withdrawing electrons from the nitrogens, which thus become partly positively charged, in turn increasing the binding energy of the electrons. Second, there is a small change in the binding energy of the nitrogen atoms in the nitro groups. Evidently, the chemical shift depends on the position of the nitro group in the molecule. There are two equivalent nitro groups in DNMN, one in NDMAN and three in PDMAN. The broad peak in NDMAN must be related to the dynamic properties of the nitro group rotating (at least partly) around the C-N bond. Third, the three apparently different -NO2 groups in PDMAN give only a slightly asymmetric peak. A similar situation is obtained for the amino nitrogens. In both proton sponges there are two independent -NMe2 groups, but

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Figure 12. N(1s) ESCA spectra of (a) DNMN, (b) DAN,(c) PSAN, (d) NDMAN, (e) PDMAN, (f) DMANH+BF4-, (g) DMANH+ClMH-, and (h) DMANH+SCN-.

their ESCA peaks are superimposed, producing a broader peak at 399.3 eV for NDMAN and PDMAN. Consider next the spectra of DAN and PSAN. Both compounds contain weak intramolecular N-H‚‚‚N hydrogen bonds. The peaks in the N(1s) spectra have shoulders and are slightly broadened. By comparison with the spectra discussed earlier, we conclude that the shoulders are due to weak hydrogen bonds rather than the number of molecules in the independent part of the unit cell. The stronger the interaction, the larger the effect, so that the peaks in both spectra are slightly shifted toward the higher binding energies by comparison with the compounds considered earlier. An even more significant effect is observed for the complexes of proton sponges: DMANH+BF4-, DMANH+ClMH-, and DMANH+NCS-, where the N(1s) peaks from the donor and acceptor atoms are clearly shifted toward higher binding energies. The peaks at higher binding energies must come from the donor atoms, and the others from the acceptor atoms. The third peak in the DMANH+NCS- spectrum comes from the nitrogen in the NCSanion and is shifted toward lower binding energies because it is easier to remove a 1s electron from a nitrogen atom in a negatively charged ion. We conclude that strong hydrogen bonds affect the core binding energies of electrons in the participating atoms and that

the difference between the binding energies of the donor and the acceptor can be used as a measure of the strength and asymmetry of strong hydrogen bonds. The binding energies of the core and valence electrons of the donor and acceptor atoms related to the binding energies in a reference system without hydrogen bonding can also be used to this end. Acknowledgment. We are grateful to the Royal Society for a Research Fellowship to K.W. and to the Department of Chemistry, University of Warsaw, for partial support from Grant 12-501/III/BST-502/24/95. Supporting Information Available: Anisotropic thermal parameters and the full geometry of the compounds investigated (8 pages). Ordering information is given on any current masthead page. References and Notes (1) Practical Surface Analysis, 2nd ed.; Briggs, D., Seah, M. P., Eds.; John Wiley: New York, 1980. (2) Barr, T. L. Modern ESCA; CRC: Boca Raton, FL, 1994. (3) Wagner, C. D.; Riggs, W. M.; Davis, L. E.; Moulder, J. F.; Muilenberg, G. E. Handbook of X-Ray Photoelectron Spectroscopy; PerkinElmer Corp.: Minnesota, 1979.

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