Substituent Effects on Intramolecular Energy Transfer. I. Absorption


W. F. Sager, N. Filipescu, and. F. A. Serafín. Table VII: Phosphorescence Spectra of Gd Chelates. Gd chelate. Xmaxi. -0. —. 0 transition-. Avp, cm...
0 downloads 0 Views 786KB Size


W. F. SAGER, N. FILIPESCU, AND F. A. SERAFIN

1092

the competition of the salt and the TDO for the water molecules.

Acknowledgment. We wish to express our appreciation to the Jersey Production Research Co. for permis-

sion to publish this work and to Dr. Walt Naegele of Esso Research and Engineering for his help in obtaining and interpreting the n.m.r. spectra. We also extend thanks to Mr. J. W. Coryell, who aided us in the cryoscopic and surface tension measurements.

Substituent Effects on Intramolecular Energy Transfer. I. Absorption and Phosphorescence Spectra of Rare Earth p-Diketone Chelates

by W. F. Sager, N. Filipescu, and F. A. Serafin Department of Chemistry, The George Washington University, Washington 6,D . C.

(Received June 1 , 1964)

The absorption and phosphorescence spectra of differently substituted rare earth @-diketonates have been investigated. The influence of the substituents on the electronic states of the organic ligand is discussed in relation to the over-all intramolecular energy migration,

Introduction Rare earth ions incorporated in organic chelates by coordination through a donor atom such as oxygen or nitrogen when excited in the region of light absorption associated primarily with the organic ligand exhibit characteristic intra-4f parity-forbidden fluorescence similar to the inorganic single crystal system. Direct excitation of the metal ion is not responsible for the line emission which, instead, is the result of an intramolecular energy transfer from the excited electronic states of the organic complex to the localized 4f energy levels of the chelated ion. The efficiency of excitation varies greatly with the nature of the ligand, temperature, and so1vent.l The over-all absorption-line emission under near-ultraviolet excitation involves (1) ground singlet -+ excited singlet absorption, (2) radiationless intersystem crossing from the excited singlet to the lowest lying triplet state, (3) transfer of energy to the chelated ion, and (4) characteristic ionic fluorescent emission. Recent studies of the emission spectra of rare earth P-diketonates have been concerned with the path of energy migration within these complex molecules.2 In these investigations only a The Journal of Physical Chemistry

restricted number of chelating agents have been studied (dibenzoylmethane, benzoylacetone, and acetylacetone). The present work is concerned with the influence of substituents attached to a 8-diketone rare earth chelate structure on the emission spectra under excitation with near-ultraviolet radiation, the intramolecular energy transfer, and the quantum states involved. The first part covers the investigation of the absorption spectra and phosphorescence spectra of a number of substituted gadolinium p-diketone chelates, indicative of the excited electronic states of the organic ligand.

Experimental Preparation of 6-Diketones. The following diketones, reagent grade, were purchased : dibenzoylmethane, benzoylacetone, theonyltrifluoroacetone, acetylacetone (1) s. I. Weissman, J . Chem. Phycr., 10,214 (1942). (2) (a) G.A. Crosby, R. E. Whan, and R. IM.Alire, ibid., 34, 743 (1961); (b) R. E. Whan and G. A. Crosby, J . Mol. Specfry.,8 , 315 (1962); (e) G.A. Crosby, R. E. Whan, and J. J. Freeman, J . Phys. Chem., 66, 2493 (1962); (d) J. J. Freeman and G. A. Crosby, ibid., 67, 2717 (1963); (e) G. A. Crosby and R. E. Whan, ibid., 36, 863 (1962).

SUBSTITUENT EFFECTS ON INTRAMOLECULAR ENERGY TRANSFER

(Eastman), trifluoroacetylacetone (K & K), hexafluoroacetylacetone (Columbia). All the other @diketones were synthesized. The symmetrically substituted dibenzoylmethanes (di-p-methoxy, di-m-methoxy, di-p-nitro, di-m-nitro, and di-p-fluoro), as well as difuroylmethane, ditheonylmethane, di-l-naphthoylmethane, and di-2-naphthoylmethane, were prepared from the acid chloride with vinyl acetate, by the procedure described by Sieglitz and Horn. Diisonicotylmethide was synthesized from 4-acetylpyridine and ethyl isonicotinate in condensation reaction with ~ o d a m i d e . ~The monosubstituted p-methoxy-, mmethoxy-, and p-phenyldibenzoylnethanes were prepared from the substituted ethyl benzoate in condensation reaction with acetophenone or the substituted acetophenone with ethyl benzoate by the sodium amide procedure. The m-nitro- and p-nitrodibenzoylmethanes were synthesized from the nitro-substituted benzoyl chloride in condensation with the sodium salt of a~etophenone.~Benzoyltrifluoroacetone was obtained from acetophenone and ethyl trifluoroacetate as described by Reid and Calvin.‘j The prepared @diketones, as well as those purchased, were distilled, sublimed, or recrystallized from appropriate solvents. Preparation of @-Diketone Chelates. Rare earth chlorides were purchased from the American Potash and Chemical Corp. (99.999% purity). The procedure involving the rare earth chloride, the @-diketone,and piperidine, as precipitating agent, in absolute ethanol was en.ployed for the preparation of most of the chelates.’ The acetylacetonates, trifluoroacetylacetonates, and hexafluoroacetylacetonates were prepared by titration with aqueous ammonia of a mixture of the diketone and the rare earth chloride in water with a pH meter in the reaction beaker, as described by Moeller and Ulrich.* The benzoylacetonates were synthesized from the sodium salt of the @-diketone and the rare earth halicie.2b The chelates were purified by washing, recrystallization, and vacuum drying for prolonged periods of time a t temperatures below decomposition. Spectroscopzc Measurements. All absorption spectra were measured in the near-ultraviolet and visible range with a Cary Model 14 recording spectrophotometer, in Spectrograde methanol at 20’. All measurements were performed on fresh solutions at concentraM in chelate. The phosphorescence tions of spectra of the gadolinium chelates were recorded on the same spectrophotometer using the fluorescence attachment. The compounds were dissolved a t a concentration Of fu10-5 in (5 parts ether, parts 3-methy1pentane, and parts ether and the methylpenThe by t a m were distilled from magnesium ethoxide. The

1093

fresh solutions of gadolinium chelates were introduced into 10-mm. quartz tubes and immersed in liquid nitrogen in a transparent quartz dewar. The frozen samples were irradiated with two sources-a beam from the internal mercury vapor lamp in the Cary Model 14 illuminating the sample from the photocell side and one from an external mercury vapor lamp 9 W, Model SL 3660 (Ultraviolet Products, Inc.) normal to the sample-slit beam. For all the aromatic b-diketone chelates, the exciting light was filtered through an aqueous CuS04 solution and a Corning 5840 filter (3000-4000 8. transmission range) whereas, for the aliphatic b-diketonates (acetylacetonates, trifluoroaceBylacetonate, and hexafluoroacetylacetonate) , the internal Cary 14 ultraviolet source was filtered through a NiS04 water solution and a Corning 9863 filter and coupled with an ext,ernal short-wave ultraviolet lamp 9 W, Model SL 2537, perpendicular to the sampleslit direction. The log scale was used on the recorder, and all the phosphorescence spectra were extrapolated to an equivalent 0.5-mm. slit for comparison. A semiquantitative evaluation of the relative intensities is possible by comparing the area under the curve of a given band on a linear relative intensity = f ( v ) scale.

Discussion Two series of @-diketonechelates have been prepared. Substituents with different configurations and electronegativities have been attached (through synthesis) in various positions, either on a dibenzoylniethide structure (series A) or directly to the @-diketonechelate ring (series B). Both symmetrically and asymmetrically substituted b-diketonates were synthesized with aromatic and/or aliphatic substituents appended to the chelating ring. Absorption Spectra in Near- Ultraviolet-Visible, The ultraviolet-visible absorption spectra of the different chelates are illustrated in Figures 2, 3, 4, and 5. The absorption spectrum of a given tris chelate did not show any significant modification on changing the metallic ion, and actually the spectrum is very similar to that of the hydrogen chelate (the [email protected]). This indicates that the absorption spectrum is characteristic of any one of the three chelate groups surrounding the ion. The molar concentration (-10-5 M ) was only approximative because analysis of chelates indicated (3) A. Sieglitz and 0. Horn, Ber., 84, 607 (1951). (4) R. Adams, “Organic Reactions,” Vol. 111, John Wiley and Sons, Inc., New York, N. Y., 1954. (5) B. 0. Linn and C. R. Hauser, J . Am. Chem. Soc., 78,6066 (1956). (6) J, C. Reid and M. Calvin, 72, 2948 (1950).

(7) G. A. Crosby and M.Kasha, Spectrochim. Acta, 10, 377 (1958). (8) T. Moeller and w. F. Ulrioh. J . horg. N ~ ~Chem., z . 2,164 (1956).

Volume 69, Number 4

April 1966

W. F. SAGER, N. FILIPESCU, ASD F. A. SERAFIN

1094

Table I Abbreviation

Series A Dibenzoylmethide p-Methoxydibenzoylmethide Di-p-methoxydibenzo ylmethide p-Xitrodibenzoylmethide Di-p-nitrodibenzo ylmethide m-Methoxydibenzoylmethide Di-m-methoxydibenzoylmethide m-Mtrodibenzoylmethide Di-m-nitrodibenzoylmethide p-Phenyldibenzoylmethide Di-p-fluorodibenzoylmethide

Z I Series A

H

/

DBM pM DpM PN DpS

mM DmM mN DmN PPh DpF

Series B Dibenzoylmethide Difuroylmethide Ditheonylmethide Diisonicotylmethide Di-1-naphthoylmethide Di-2-naphthoylmethide Theonyltrifluoroacetonate Benzoylacetonate Acetylacetonate Trifluoroacetylacetonate Hexafluoroacetylacetonate

DBM DFuM DTM DPyM DlNM D2NM TTA BA AcA TFAcA HFAcA

C ‘

‘H Series B Figure 1. Substituted p-diketone tris chelates.

departure from the exact empirical formula. Therefore, no accurate extinction coefficient measurement was possible. The predominant feature of the ultraviolet absorption spectra of the tris diketonates studied is the strong band occurring usually from 280 to 380 nip. This band is due to the same kind of electronic transition in each case, probably a T-T* type or “K” transition associated with the conjugated system. R\

H-C R’

c=ok

/

\\

?l/3

,c-0

This system in which. R and R’ represent the diff erent substituents attached to the P-diketone ring is coninion to all of the investigated chelates. The sixThe Journal of Physical Chemistry

200

250

300

350

Wave length, me.

400

450

Figure 2. Absorption spectra: A, dibenzoylmethides; B, p-methoxydibenzoylmethides; C, p-nitrodibenzoylmethides; D, m-methoxydibenzoylmethides; E, m-nitrodibenzoylmethides.

melnber enolate ring is planar and has a Cpv syiiinietry if R = R’; the pairs of M-0, 0-C, and C-C distances are of equal length with C-C and C-0 dihtances of 1.39 and 1.28 8. intermediate between single and double bonds.g There is some evidencelo that an enolate type (9) R. B.Roof, Acta Cryst., 9 , 781 (1956) (10) R. H. Holm and F. A. Cotton, J . Am. Chem. SOC.,80, 5658 (1958).

1095

SUBSTITUENT EFFECTS ON INTRAMOLECULAR ENERGY TRANSFER

Table I1 M3+chelate mp

, , . ,A

200

250

DBM 363

pM 358

300 350 Wave length, mp.

DpM 364

400

DpN 362

pN 352

450

Figure 3. Absorption spectra: A, dibensoylmethides; F, dianisoylmethides; G, di-p-nitrodibenzoylmethides; H, di-m-methoxydibenzoylmethides; I, di-m-nitrodibenzoylmethides.

nM 355

DmM 352

mN 353

DmN 363

pPh 355

DpF 350

with the 7r-electrons of the ligand (oxygen atoms) are the empty 5dzz,5d,,, and 5dz, orbitals. In series A (meta- and para-substituted dibenzoylmethides), the main absorption peak (Amax) is found a t longer wave lengths than in acetylacetonates or other aliphatic substituted 6-diketonates, as expected on increasing the length of the conjugated system as a whole, compared to enol resonance alone in the acetylacetonates. para substitution shifts the main molecular absorption peak toward red for both CHsO and SO2 groups, in monosubstituted and (more) in disubstituted dibenzoylmethides. Di-p-fluoro and p-phenyl substitution results also in a bathochroniic shift compared to the monosubstituted chelates. Rlethoxy or nitro groups substituted in para position accept the positive charge more easily on the ether oxygen or on the nitrogen atom, respectively. These polar configurations represent cross conjugation and compete with the enolate ring resonance, thereby decreasing the stabilization of the ground state and resulting in a net bathochromic shift for A,, in absorption.

Table I11 M3+ chelate mfi

, , ,A

200

250

300

350

Wave length, mp.

400

450

Figure 4. Absorption spectra: A, dibenzoylmethides; J, difuroylmethides; K, di-1-naphthoylmethides; L, di-2-naphthoylmethides; M, p-phenyldibenzoylmethides; N, di-p-fluorodibenzoylmethides; 0, ditheonylmethides.

resonance tends to equalize the pairs of C-C, M-0, and C-0 distances although a benzoid resonance has also been suggested for the P-diketonate ring. Six oxygen atoms of the ligand octahedrally surround the trivalent rare earth ion, and the ion uses d2sp3type hybrid orbitals to form six bonds with the nearest neighbors, formed by hybridization of 5d22-y2, 5dz2, 6s, 6p, 6p,, and 6p, orbitals. The metal orbitals available for a-bonding

DBM 343

pM 358

DpM 364

DBM 343

pN 352

DpN 362

The effect of para substituents on the location of the main molecular absorption peak is smaller than the effect of substituents on the absorption spectra of most benzene derivatives." This indicates a limited resonance interaction between substituents attached to the dibenzoylmethide system and the chelated enolate ring. The fact that the di-para-substituted dibenzoylmethides have the absorption maxima at longer wave lengths than the mono-pura-substi tuted chelates, which in turn show a bathochromic shift with regard to the unsubstituted dibenzoylmethide, implies that introduction of the first group induces only a small asymmetry in the enolate ring. This asymmetry has a restricted effect on the energetic location of the excited singlet but plays an important role in the fluores(11) (a) L. Doub and J. M. Vandenbelt. J . Am. Chem. Soc., 69,2714 (1947); 71, 2414 (1949); (b) G . S. Hammond. W. G. Borduin, and

G. A. Guter, ibid., 81, 4682 (1959).

Volume 69,.Yumber 4

April 1966

W. F. SAGER,N. FILIPESCU, AND F. A. SERAFIN

1096

cent emission of the chelated ion when transfer of energy to the ion is possible. The fact that some of the resonance structures mentioned increase the availability of electrons at the carbonyl oxygen does not imply an increased stabilization of the ground state, just as substitution of a niethoxy group for a methyl in cross conjugation with C=O in acetylacetonate decreases the stability of the chelate. Fluorine and phenyl para substitution on dibenzoylmethide results also in a bathochromic shift for the same reason. The

Table IV

200

M * +chelate Xnmm

DBM 343

w

DpF 350

pPh 355

250

300 350 W a v e length, mg.

400

450

Figure 5 . Absorption spectra: A, dibenzoylmethides; P, benzoylacetonates; Q, acetylacetonates; R, trifluoroacetylacetonates; S, hexafluoroacetylacetonates; T, theonyltrifluoroacetonates; U, benzoyltrifluoroacetonates.

meta substitution of CHZO and NO2 shifts A,, toward the red less significantly than does para substitution, and the shift is more pronounced for mono- than for di-meta-subst,ituted dibenzoylniethides. Only inductive effects can be at.tributed to meta substituents. For series B , A,, values of the main absorption band are given in Table V.

served for A,, from acetylacetonate to trifluoroacetylacetonate and hexafluoroacetylacetonate. This shift can be accounted for by assuming that the introduction of the electronegative fluorine causes an increase in the contribution of the ionic resonance forms in the excited

Table V M*+chelate X,.,

-

w

DTM 375

DFuM 372

D2NiM 372

DPyM 363

DlNhl 346

The aromatic substituents on p-diketone chelates (DFuRI, DTRI, D l N M , D2N,111 and DPyRI) determine a red shift for A, compared to DBRl owing to an increased resonance with the substituents: for D l N M and D2NM analogous to pPh, and for DFuM, DTM, and DPyM, the polarity of the heteroatom enhances the contribution of polar structures resulting in a destabilization of the ground state through interference with resonance in the enolate ring. Less competition with the chelate ring resonance expected for aliphatic substituents results in a hypsochromic shift

Table VI M z +chelate x

~ mg ~

DRM

~ 343,

TTA 340

BT.4

BA

325

323

HFAcA 304

TFAcA 294

Ac.4 293

for A,,. There are a few published data on the effect of fluorine substitution in aliphatic p-diketones on the absorption spectra.6,10j12A continuous red shift was obThe ,Journal of Physical Chemistry

DBM 343

TTA 340

BTA 325

BA 323

HFAcA 304

TFAcA 294

AcA 293

states which stabilize this state reducing the energy difference between the excited and ground states. Phosphorescence Spectra of Gadolinium Chelates. Gadolinium chelates were selected for the determination of phosphorescence spectra owing to enhanced phosphorescence-fluorescence ratios (&,/+* > 100) compared to those of other lanthanide chelates. The strong phosphorescence from Gd chelates is justified by the absence of any ionic resonance level below the triplet state of the chelates, coupled with the strong paramagnetic effect of the Gd ion. Electric dipole and magnetic dipole transitions between pure singlet and pure triplet states are rigorously forbidden on account of the orthogonality of the spin-wave functions. The intervention of spin-orbit coupling (introduced by atoms with high atomic number and by paramagnetic atoms) brings about a mixing of singlet and triplet states, destroying their purity and permitting inter(12) R. L. Belford. A. E. Martell, and 31. Calvin, J . Inorg. A'ucl. Chem., 2 , 1 1 (1956); E. M . Larsen, G. Terry, and J. Leddy, J . A m . Chem. Soc.. 7 5 , 5107 (1953).

SUBSTITUENT EFFECTS O N INTRAMOLECULAR ENERGY TRANSFER

1097

>; .r

z

3

.-C W

-e

." e

M i

4000

4500

5000 IVave length,

5500

6000

A.

Figure 6. Phosphorescence spectra (Gd chelates): A, dibenzoylmethide ; B, p-methoxydibenzoylmethide; C, p-nitrodibenzoylmethide ; D, m-methoxydibenzoylmethide; E, m-nitrodibenzoylmethide.

4000

4500

5000 W a v e length,

5500

4000

5000

4500

Wave length,

5500

6000

A.

Figure 8. Phosphorescence spectra (Gd chelates): A, dibenzoylmethide; J, difuroylmethide; K, di-1-naphthoylmethide; L, di-2-naphthoylmethide ; M,p-phenyldibenzoylmethide; N, di-p-fluorodibenzoylmethide; 0, ditheonylmethide.

6000

A.

Figure 7. Phosphorescence spectra (Gd chelates): A, dibenzoylmethide ; F, di-p-methoxydibenzoylmethide; G, di-p-nitrodibenzoylmethide; H, di-m-methoxydibenzoylmethide; I, di-m-nitrodibenzoylmethide.

combinations between nominal singlet and triplet states.l3 Most of the triplet excitation occurs by intersystem crossing from the excited singlet. This radiationless transition is significantly increased under the perturbation effects introduced by the electric and magnetic fields of the heavy paramagnetic gadolinium ion. The emission from gadolinium p-diketonates consists essentially of phosphorescence, with the exception of DpM, DmM, pPh, DpN, and DPyhl,

4000

3500

4500

5000

W a v e length,

5500

6000

A.

Figure 9. Phosphorescence spectra (Gd chelates): A, dibenzoylmethide; P, benzoylacetonate; Q, acetylacetonate; R, trifluoroacetylacetonate; S, hexafluoroacetylacetonate; T,theonyltrifluoroacetonate; U, benzoyltrifluoroacetonate; V, dipyridoylmethide.

which exhibited some fluorescence a t shorter wave length. The phosphorescence band emission was well defined, and the bands represent the fall from the phosphorescent state to a riuiiiber of vibrational states of the ground state. Two clearly defined bands ~~

~

(13) (a) M . Kasha and S. P. McGlynn, Ann. Rev. Phys. Chem., 1, 403 (1956); (b) M.Kasha, Discussions Faraday Soc., 9, 14 (1950).

Volume 69, .\'umber

4

April 1965

W. F. SAGER, N. FILIPESCU, AND F. A. SERAFIN

1098

Table VI1 : Phosphorescence Spectra of Gd Chelates Gd chelate

b”,mp

DBM Phf DpM PN DpX mM DmM mN DmN PPh DPF DFuM DTM DlNM

492 485 477 506 536 493 493 498 502 498 482 493 513 522 518 480 470 465 492 394 437 452

DBNM DPyM BA BTA TTA AcA TFAcA HFAcA

0 + 0 transition 5,, cm.-’ Ai,, om.-’

20,300 20,700 21,000 19,700 18,600 20,300 20,300 20,100 19,900 20,100 20,800 20,300 19,500 19,100 19,300 20,800 21,200 21,500 20,400 25,300 22,800 22,200

420 440 560 1800 1400 440 800 460 420 800 400 320 260 800 420 640 440 440 440 800 720 440

are observed for all chelates investigated (a third band of lower intensity was recorded for several chelates). The band a t shorter wave length is assumed while the second band to be the 0 -+ 0 transitionZa~b~‘* takes the 0 + 1 designation, representing the transition from the lowest triplet state to a vibrationally excited ground state. The fact that the 0 + 0 band is the strongest and relatively sharp indicates that, according to the Franck-Condon principle, the phosphorescent state does not differ greatly from the ground state in size or in shape, reflected in high probability of direct transition from T to SO without vibration. This assumption can be made considering that the phosphorescent state is practically vibrationless at liquid nitrogen temperature. The frequency differences between the 0 + 0 and 0 + l bands vary from 1100 l o 1600 cni. -1 in the investigated chelates. This separation coincides with the infrared absorption frequency range found by some investigators for the C-0 or C-C bond in ,$-diketone chelates. l5 The vibration frequency may be indicative of the intermediate singledouble bond character of the C-0 or C-C bonds in these compounds. The triplet state is associated with a biradical structure formed by the separation (with parallel spin) of two electrons of a double bond. These two odd electrons repel each other, and in a conjugated system they tend to arrange as far apart as allowed by The Journal of Physical Chemistry

-

A E R . kcal.

-22.8 -21.7 -20.5 -20.5 -24.8 -22.8 -21.7 -23.4 -23.8 -22.4 -21.5 -23.0 -25.6 -25.2 -25.7 -20.8 -20.3 -19.4 -22.5 - 7.5 -14.8 -17.4

-0 + 1 transition-b”,m r !,‘, cm. -’

523 517 509 542 570 523 520 529 534 525 513 530 554 555 554 508 498 493 532 412 462 482

19,100 19,300 19,600 18,500 17,500 19,100 19,200 18,900 18,700 19,000 19,500 18,800 18,000 18,000 18,000 20,800 20,000 20,300 18,800 24,300 21,700 20,800

ai

=

i,

- i,’,

cm.-1

1200 1400 1400 1200 1100 1200 1100 1200 1200 1100 1300 1500 1500 1100 1300 1100 1200 1200 1600 1000 1100 1400

resonance to a configuration giving the most important contribution to the description of the lowest triplet. The evaluation of AER (the resonance energy in the ground singlet less the resonance energy in the triplet state) has been made using the relation AER = (iip Aii,)hc - B where I, is the frequency of the 0 + 0 band at the peak, Aiip is the “half-width” of the same band, and B is the value for breaking the C=O bond, taken as 82 kcal.I4 The values for AERvary from -7.5 kcal. for AcA to -25.7 kcal. for D2NM. These negative values of AER could be interpreted as resulting from a significant odd-electron resonance in the triplet state. Resonance in the triplet state of a dibenzoylmethide involving para substituents (both CHIO and NOz) can be considered as localizing one of the odd electrons on the substituent, while the other is primarily found on one of the two P-diketone oxygen atoms. The strong acid auxochrome nitro group in para position lowers the energy of the triplet state considerably whereas, in meta, the same trend is smaller owing only to an is observed induct’ive effect. An opposite shift in A,, for the basic auxochrome niethoxy-substituted dibenzoylmethides. Di-p-fluoro substitution on di-

+

(14) G. N. Lewis and M.Kasha, J . Am. Chem. Soc., 66, 2100 (1944). (15) (a) L. J. Bellamy and R. F. Branch, J . Chem. Soc., 4491 (1954); (b) J. Lecompte, Discussions Faraday Soe., 9, 125 (1950).

SUBSTITUENT EFFECTSON INTRAMOLECULAR ENERGY TRANSFER

1099

Table VI11 : Relative Intensities of Phosphorescence Spectra Gd

Avo-0,

chelate

cm.

DBM PM Dp-M PN DPN mM DmM

mS DmN PPh DPF DFuM DTM DlSM D2SM DPyM TTA BTA BA 4cA TFAcA HFAcA a

-1

1400 1400 1400 2200 2400 1400 1400 1400 1400 1400 1200 1000 1200 I400 I400 1400 1400 1400 1400 1400 1400 1400

Recorder units.

Av'o-o,

hmsx, 0

-

0,

Rel. int. 0

-

0,

1,

A.U.*

cm.-l

cm.-1

A.U.

420 440 560 1800 1400 440 800 460 420 800 400 320 260 800 420 620 440 440 440 800 720 440

103.6 103.5 102.6 100.26 101.6 102.1 100.8 102.7 102.3 101.1 103,3 102.1 103.2 10 102.1 101.1 103 103 102.6

2,229,920 1,802,340 251,200 2,900 52,000 71,820 3,000 290,580 112,000 9,800 997,500 51,700 682,000 8,000 70,560 8,550 570,000 226,860 570,000 237,000 141,800 570,000

1400 1200 1200 1400 2000 1400 1400 1400 1400 1400 1400 1400 1000 1600 1200 1600 1400 1200 1200 1400 1600 1400

640 680 680 1000 1000 720 600 640 640 800 640 800 460 720 640 800 720 800 720 800 800 720

1,061,950 806,400 101,300 850 7,950 22,720 1,300 134,000 33,500 2,950 670,000 14,960 95,550 3,040 9,920 2,560 224,360 70,000 208,560 75,000 101,000 282,580

102.6

102.3 103

Total rel. int., A.U.

3,291,870 2,608,740 352,500 3 ,750 59,950 94,540 4,300 424,580 145,500 12,750 1,667,500 66,660 777,550 11,040 80,480 11,110 794,360 296,860 778,560 312,000 242,800 852,580

' Arbitrary units.

< p3I < DBM < pX < DpN mM DBRl < mN < DmN DmlM DpF < DBM < pPh DPyM < DB3I < DFuR4 < DTM < D2NM