Through-space Research Articles

Enhanced hyperpolarizability via electron correlations in donor-σ-acceptor systems

Ab initio calculations demonstrate that specific zwitterionic molecules which have a $\ensuremath{\sigma}$-bonded donor-acceptor system show an enhanced hyperpolarizability $(\ensuremath{\beta})$ value when the effects of electron correlations are considered. Ab initio second-order M\o{}ller-Plesset perturbation theory (MP2) through-space (TS)--through-bond (TB) interaction (TB denotes orbital interactions through directly bonded atoms in a molecule, and TS denotes all interactions other than TB interactions) analysis proposes that the $\ensuremath{\sigma}$ conjugation between acceptor and donor through bonds causes the dependence of the perturbation term between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (and their vicinal molecular orbitals) in MP2 calculations on electric fields, making the hyperpolarizability $(\ensuremath{\beta})$ value remarkably large.

U-Shaped Donor [Bridge] Acceptor Systems with Remarkable Charge Transfer Fluorescent Properties: An Experimental and Computational Investigation

The photoinduced intramolecular electron transfer in two donor−bridge−acceptor systems was studied using (time-resolved) fluorescence and transient absorption techniques. DPN[8cy]DCV and DPMN[8cy]DCV consist of a 1,4-diphenylnaphthalene (DPN) and a 1,4-diphenyl-5,8-dimethoxynaphthalene (DPMN) electron donor, respectively, and the 1,1-dicyanovinyl acceptor (DCV) in both systems. The overall geometry of the saturated hydrocarbon bridge is U-shaped, separating the donor and acceptor by an 8-σ-bond through-bond distance and a 5.8 Å (center-to-center) through-space distance in the ground state. In all solvents fast electron transfer is observed in both systems resulting in a fluorescent charge transfer (CT) state. Especially for DPN[8cy]DCV CT fluorescence can be detected over a wide range of solvent polarity. The solvent dependence of the CT fluorescence position, lifetime, and quantum yield could thus be employed to estimate the solvent effect on the dipole moment of the CT state, the rate of charge recombination, and the electronic coupling (V) between donor and acceptor. It is concluded that in the (luminescent) CT state both the distance between donor and acceptor and their electronic coupling are virtually solvent independent, which excludes a solvent-mediated electron-transfer pathway. Gas phase (U)HF ab initio MO calculations carried out on the model molecule DMN[8cy]DCV (which contains a computationally less demanding 1,4-dimethoxynaphthalene donor) predict that the center-to-center distance between the two chromophores in the CT state is about 4.4 Å which amounts to a 1.4 Å contraction with respect to the ground state geometry. The degree of contraction is almost entirely due to pyramidalization at the DCV radical anion site and occurs in the direction of the dimethoxynaphthalene radical cation for electrostatic reasons. The calculated weak out-of-plane bending potential associated with this pyramidalization implies that the degree and direction of pyramidalization in the CT state of the DCV moiety can be preserved in solution and that it is fairly insensitive toward solvent polarity as shown by the results of UHF/6-31G(d) continuum solvation calculations and as supported by the experimental results for DPN[8cy]DCV. The small and constant D/A separation in the CT state also explains the experimentally found constancy of the electronic coupling, which must be of a direct through-space (TS) nature because no solvent molecules can be accommodated between D and A. Remarkably, while the charge recombination in DPMN[8cy]DCV displays the strong rate enhancement with increasing solvent polarity typical for charge recombination occurring under “inverted region conditions”, the rate of charge recombination in DPN[8cy]DCV is virtually constant over a wide range of solvent polarities. This very unusual behavior appears to be related to the presence of parallel charge recombination pathways to respectively the ground state and to a local triplet state with an opposite solvent dependence of their rate.

Transannular interaction in bifunctional olefins and ketones: A semiempirical electron density analysis

Electron densities on the olefinic carbons of some dimethylene compounds are calculated by semiempirical model PM3, and the values are compared with those of the corresponding monomethylene compounds. A relationship is observed between the change of electron density Δ(C) and the change of 13C NMR chemical shift Δδ. A correlation is also found between Δ(C) and Δ(O), i.e. the carbon and oxygen atoms, of methylene-ketones. The electron density differences are induced by three types of transannular interactions: electrostatic force, orbital interactions through bond (TB) and orbital interactions through space (TS). Electrostatic force is the most prominent factor for ketones in which the high polarity of carbonyl group can apply a strong field effect onto nearby atoms. For nonpolar methylene groups, orbital interactions can be transmitted either TS or TB more effectively than electrostatic force. A conformational analysis, performed on a dimethylene compound 4e, confirms the existence of TS interaction between the double bonds.

Stabilized Koopmans' Theorem Calculations on the π* Anion States of 1,4,5,8-Tetrahydronaphthalene

The exponent stabilized Koopmans' theorem is used to calculate the energies of the π* anion states of 1,4,5,8-tetrahydronaphthalene. The results indicate that the ordering of π* anion states is 2 2B3g < 2 2Au < 3 2B3g. This order of anion states is the same as that which would prevail were only through-space (TS) interactions present. The through-bond (TB) interactions destabilize all the π* orbitals; however, they do not change the order.

Superexchange Coupling and Electron Transfer in Large Molecules: Through-Space and Through-Bond Interactions

The superexchange coupling (TDA) between distant donor−acceptor (D−A) redox centers in large electron-transfer (ET) molecules, such as proteins, involves through-space (TS) as well as through-bond (TB) interactions. For these complex systems, the analysis of TDA either in terms of an electron tunneling through a potential energy barrier or in terms of an electronic-coupling pathway model may be inappropriate or, at best, requires some justification. From an analytical and numerical study of TDA in a folded random chain system, we clarify the role of both TS and TB interactions. For this molecular model system, we find that a proper description of ET processes requires both a renormalization of the medium orbital energies by TB interactions and, beyond any perturbative approach, a full account of TS couplings. Except under extreme energetic conditions, neither TB nor TS interactions alone are able to describe the complete behavior of the superexchange coupling. Depending on the relative signs of some parameters, such as the energy gap and the TS and TB electronic couplings, very distinct behaviors of TDA are obtained.

A cautionary comment on the use of orthogonal localized molecular orbitals for the quantitative analysis of through-space and through-bond orbital interactions

The quantitative dissection of orbital interactions into through-space (TS) and through–bond (TB) contributions using orthogonal localized MOs (LMOs), as originally proposed by Heilbronner and Schmelzer, is critically discussed, using as a test case, cyclohexa-1,4-diene. It was found that the (HF/STO-3G) TS interaction energies for this molecule, obtained using three different orbital localization procedures (Foster–Boys, the Weinhold natural bond orbitals and the Weinhold natural localized orbitals) are unsatisfactory in the sense that the calculations give a relatively small splitting between the π+ and π– orbitals and an inverted sequence of π* orbitals resulting from supposedly pure TS interactions. This result contradicts the Hoffmann conceptual model of orbital interactions. The source of the problem is traced to the presence of the ‘orthogonalization’ tails associated with the LMOs. An alternative strategy for dissecting orbital interactions, termed the ‘cluster’ approach is discussed using an ethene dimer model as an example.

Photoelectron spectra, electronic structure and long-range electronic interaction in some steroids

Abstract

Through-Space Transmission of 19F-13C Coupling Via an Intermediate Bond. An Experimental and Theoretical Study

In order to obtain a deeper insight into the title effect, several compounds with an F atom very close to a C-H of a nearby functional group were synthesized and the relevant couplings measured. The most conspicuous case was that of 8-fluoro-2-hydroxynaphthalene-1-carbaldehyde where a close proximity between the F and H atoms is the result of fluorine-oxygen repulsion and the formation of an intramolecular hydrogen bond between the hydroxyl and carbonyl groups. The experimental four-bond J(F,CHO) coupling is 26.2 Hz. A compound very similar to this one, but without the OH group, was chosen on which to perform a polarization propagator analysis of the through-space (TS) coupling pathways, at the RPA-INDO level. The expression for the TS coupling in terms of the projected polarization propagator and perturbators was numerically analysed. It is found that this coupling is completely dominated by a TS component of the Fermi contact (FC) term, the main features of which are: ( i ) It decays exponentially with the F-H distance; (ii) Its main contribution comes from an electron excitation involving the F lone-pair, the C-H bond of the CHO moiety and its corresponding antibonding orbital;(iii) The π-type lone-pair does not contribute to the TS coupling pathway of the FC term.

How restricted are partially restricted mo calculations? A few comments on the calculations of spin-spin coupling pathways at the INDO/FPT level

While standard FPT/INDO MO calculations are widely used, and are sometimes useful in the prediction of conformational or structural behavior of spin-spin couplings, a more detailed and informative picture can be obtained if the total coupling is divided into ?r, u, TS (through space), and other specific contributions. The history of the calculations was reviewed by Kowalewski (I). Recently, Engelmann et al. (2) and Fukui et al. (3) developed the PRMO and SOS2 methods. The NNBI procedure, especially useful in the calculation of TS contributions, was described by Barlield (4). Attempts to apply PRMO to the interpretation of TS components of several H-H, H-F, and H-C couplings, and some important differences found between PRMO and NNBI results, led to the calculations described in this report. Its purpose is to point out that when the TS contribution is computed by the PRMO method, setting some atomic orbitals to be restricted, the contribution so obtained may often contain a large component due to the change in the spin polarizability near the perturbed nuclei. A few examples are discussed, PRMO and NNBI methods are compared, and the meaning of the ?r contribution is briefly discussed. The computations utilized an Amdahl 47O/V7 with a program modified from CNIND0/74 (QCPE 28 1) by the author. All the calculations mentioned in this report are routinely carried out by the program. Standard geometry was mostly used. The geometry of anisole was that previously described (5). The most serious problem with the PRMO method, in addition to those mentioned by the authors (2, 6, 7), occurs in the calculations of TS pathways. For example, if the PRMO values of the TS contributions in the HO-H*. . . HCH3 complex (where H* is the perturbed atom) are computed (setting the HO fragment restricted) we unexpectedly find that the pathways H* OH CH4 are very important (the residual couplings between H* and CH4 carbon and the nearest proton are only a small fraction of the original values). And, by setting the Fock elements between OH and CH4 zero (this is the NNBI (4) method) no significant differences between the standard INDO/FPT and these results are seen. The numerical results are shown in Table 1. The strange PRMO results can be easily explained: restricting the OH fragment makes the environment of the OH proton less polarizable and this reduces its

ChemInform Abstract: THROUGH BOND AND THROUGH SPACE INTERACTIONS IN THE PHOTODIMERS OF ACENAPHTHYLENE

Chemischer InformationsdienstVolume 14, Issue 8 Physical Organic Chemistry ChemInform Abstract: THROUGH BOND AND THROUGH SPACE INTERACTIONS IN THE PHOTODIMERS OF ACENAPHTHYLENE R. GLEITER, R. GLEITERSearch for more papers by this authorK. GUBERNATOR, K. GUBERNATORSearch for more papers by this author R. GLEITER, R. GLEITERSearch for more papers by this authorK. GUBERNATOR, K. GUBERNATORSearch for more papers by this author First published: February 22, 1983 https://doi.org/10.1002/chin.198308062AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume14, Issue8February 22, 1983 RelatedInformation

ChemInform Abstract: ′THROUGH SPACE′ AND ′THROUGH BOND′ INTERACTIONS IN (2.2)CYCLOPHANES; THE ASSIGNMENT OF THEIR PHOTOELECTRON SPECTRA

Chemischer InformationsdienstVolume 12, Issue 25 Physical Organic Chemistry ChemInform Abstract: ′THROUGH SPACE′ AND ′THROUGH BOND′ INTERACTIONS IN (2.2)CYCLOPHANES; THE ASSIGNMENT OF THEIR PHOTOELECTRON SPECTRA B. KOVAC, B. KOVACSearch for more papers by this authorM. ALLAN, M. ALLANSearch for more papers by this authorE. HEILBRONNER, E. HEILBRONNERSearch for more papers by this author B. KOVAC, B. KOVACSearch for more papers by this authorM. ALLAN, M. ALLANSearch for more papers by this authorE. HEILBRONNER, E. HEILBRONNERSearch for more papers by this author First published: June 23, 1981 https://doi.org/10.1002/chin.198125045Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue25June 23, 1981 RelatedInformation

ChemInform Abstract: THE UV SPECTRA OF 3‐KETO‐Δ4,8(14)‐STEROIDS AS AN EXAMPLE OF THROUGH SPACE CONJUGATION

Chemischer InformationsdienstVolume 11, Issue 2 Physical Organic Chemistry ChemInform Abstract: THE UV SPECTRA OF 3-KETO-Δ4,8(14)-STEROIDS AS AN EXAMPLE OF THROUGH SPACE CONJUGATION E. C. HERRMANN, E. C. HERRMANNSearch for more papers by this authorG.-A. HOYER, G.-A. HOYERSearch for more papers by this author E. C. HERRMANN, E. C. HERRMANNSearch for more papers by this authorG.-A. HOYER, G.-A. HOYERSearch for more papers by this author First published: January 15, 1980 https://doi.org/10.1002/chin.198002046AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume11, Issue2January 15, 1980 RelatedInformation

ChemInform Abstract: ROLE OF THROUGH SPACE 2P‐3D OVERLAP IN THE ALKYLATION OF PHOSPHINES

Chemischer InformationsdienstVolume 10, Issue 6 Organoelement Compounds ChemInform Abstract: ROLE OF THROUGH SPACE 2P-3D OVERLAP IN THE ALKYLATION OF PHOSPHINES W. E. MCEWEN, W. E. MCEWENSearch for more papers by this authorA. B. JANES, A. B. JANESSearch for more papers by this authorJ. W. KNAPCZYK, J. W. KNAPCZYKSearch for more papers by this authorV. L. KYLLINGSTAD, V. L. KYLLINGSTADSearch for more papers by this authorW.-I. SHIAU, W.-I. SHIAUSearch for more papers by this authorS. SHORE, S. SHORESearch for more papers by this authorJ. H. SMITH, J. H. SMITHSearch for more papers by this author W. E. MCEWEN, W. E. MCEWENSearch for more papers by this authorA. B. JANES, A. B. JANESSearch for more papers by this authorJ. W. KNAPCZYK, J. W. KNAPCZYKSearch for more papers by this authorV. L. KYLLINGSTAD, V. L. KYLLINGSTADSearch for more papers by this authorW.-I. SHIAU, W.-I. SHIAUSearch for more papers by this authorS. SHORE, S. SHORESearch for more papers by this authorJ. H. SMITH, J. H. SMITHSearch for more papers by this author First published: February 6, 1979 https://doi.org/10.1002/chin.197906216AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume10, Issue6February 6, 1979 RelatedInformation