Small hydrocarbon cyclophanes: Synthesis, X-ray analysis and molecular modelling
Small hydrocarbon cyclophanes, such as [2.2.0]m,m,m-cyclophane (20) and [2.2.0]p,m,m-cyclophane (21), are strained analogues of the well-known π-prismand [2.2.2]p,p,p-cyclophane (1). The synthetic route to these molecules is based on well-established cyclophane methodology which offers a general access to a whole family of hydrocarbon cyclophanes. Single crystal X-ray analysis and molecular modelling showed that the reduction of the ring size from 18-membered (1) to 14-membered (21) or 13-membered (20) has a substantial effect on the size and the shape of the cyclophane’s cavity, thus blocking its ability to complex Ag+ ions. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
Pyrene derived functionalized low molecular weight organic gelators and gels
Pyrene derived binary functionalized low molecular weight organic gelators (FLMOGs) and gels thereof in selected organic solvents were synthesized and characterized. The functionality refers to a functional group that does not take part in formation of the supramolecular gel network, but remains free and available for other purposes, such as to bind nanoparticles or other molecules into the gel structure. Functional groups were observed to disturb gel formation strongly, if they interact with each other within the same supramolecule due to the formation of competitive structures. Preventing such interactions restored the original gel properties. A gel with weaker supramolecular bonding than…
Study of Mechanisms of Light-Induced Dissociation of Ru(dcbpy)(CO)2I2 in Solution down to 20 fs Time Resolution
Mechanisms of the light-induced ligand exchange reaction of (trans-I) Ru(dcbpy)(CO)2I2 (dcbpy = 4,4'-dicarboxylic acid-2,2'-bipyridine) in ethanol have been studied by transient absorption spectroscopy. Ultraviolet 20 fs excitation pulses centered at 325 nm were used to populate a vibrationally hot excited pi bipyridyl state of the reactant that quickly relaxes to a dissociative Ru-I state resulting in the release of one of the carbonyl groups. Quantum yield measurements have indicated that about 40% of the initially exited reactant molecules form the final photoproduct. A 62 fs rise component in the transient absorption (TA) signal was observed at all probe wavelengths in the visible regio…
Spectroscopic and quantum chemical study of pressure effects on solvated chlorophyll
Abstract Hydrostatic pressure effects up to 907 MPa on absorption spectra of chlorophyll a molecules dissolved in diethyl ether have been studied at ambient temperature both experimentally and theoretically using quantum chemistry methods. The fluorescence spectra are studied only experimentally. The data suggest that coordination interactions between the central Mg atom of the chlorophyll and solvent molecules along with interactions that modify the porphyrin skeleton of the solute are responsible for the observed differences of pressure dependence of the Q y , Q x , and Soret spectral bands. The coordination number of the Mg atom changes from five to six between 400 and 600 MPa.
1H, 13C and 15N NMR spectral and theoretical studies of some methyl and alkylamino derivatives of 4-halopyridine N-oxides
Abstract Nine new and three earlier known 4-halogen (Cl and Br) substituted pyridine N-oxides have been prepared and their 1 H, 13 C and 15 N NMR chemical shifts assigned based on PFG 1 H, X (X= 13 C and 15 N) HMQC and HMBC experiments as well as the comparison with our earlier results for substituted pyridine N-oxide derivatives. The 15 N resonances of the pyridine nitrogen are 27–40 ppm more shielded in 4-halo-2-alkylamino-6-methyl-5-nitropyridine N-oxide than in parent 4-halopyridine N-oxide. According to quantum chemical ab initio HF/6-311G** calculations the amino tautomer of 4-chloro-2-methylamino-6-methyl-5-nitropyridine N-oxide is more stable than its imino form. Using B3LYP/6-311G*…
E-2-Benzylidenebenzocycloalkanones III. Studies on transmission of substituent effects on IR carbonyl stretching frequencies and 13C NMR chemical shifts of E-2-(X-benzylidene)-1-indanones. Comparison with the IR data of E-2-(X-benzylidene)-1-indanones, -tetralones, and -benzosuberones
Abstract Single substituent parameter and dual substituent parameter analysis was applied to study transmission of substituent effects on IR carbonyl stretching frequencies of E -2-(X-benzylidene)-1-indanones ( 3 ), -tetralones ( 4 ), and -benzosuberones ( 5 ). Similar analyses were performed for selected 13 C NMR chemical shifts of some E -2-(X-benzylidene)-1-indanones ( 3 ). For a better understanding of the results semiempirical and ab initio quantum chemical calculations were performed to determine the preferred geometry and to calculate the theoretical 13 C NMR chemical shifts of the selected compounds ( 3 ). The differences among the regression coefficients were discussed in terms of …
Excitation Energy Transfer in Isolated Chlorosomes from Chlorobaculum tepidum and Prosthecochloris aestuarii
Excitation energy transfer in chlorosomes from photosynthetic green sulfur bacteria, Chlorobaculum (Cba.) tepidum and Prosthecochloris (Pst.) aestuarii, have been studied at room temperature by time-resolved femtosecond transient absorption spectroscopy. Bleach rise times from 117 to 270 fs resolved for both chlorosomes reflect extremely efficient intrachlorosomal energy transfer. Bleach relaxation times, from 1 to 3 ps and 25 to 35 ps, probed at 758 nm were tentatively assigned to intrachlorosomal energy transfer based on amplitude changes of the global fits and model calculations. The anisotropy decay constant of about 1 ps resolved at 807 nm probe wavelength for the chlorosomes from Chlo…
Superchiral Pd 3 L 6 Coordination Complex and Its Reversible Structural Conversion into Pd 3 L 3 Cl 6 Metallocycles
Large, non-symmetrical, inherently chiral bispyridyl ligand L derived from natural ursodeoxycholic bile acid was used for square-planar coordination of tetravalent Pd(II) , yielding the cationic single enantiomer of superchiral coordination complex 1 Pd3 L6 containing 60 well-defined chiral centers in its flower-like structure. Complex 1 can readily be transformed by addition of chloride into a smaller enantiomerically pure cyclic trimer 2 Pd3 L3 Cl6 containing 30 chiral centers. This transformation is reversible and can be restored by the addition of silver cations. Furthermore, a mixture of two constitutional isomers of trimer, 2 and 2', and dimer, 3 and 3', can be obtained directly from …
Spectroscopic Properties of Mg−Chlorin, Mg−Bacteriochlorin, and Bacteriochlorophylls a, b, c, d, e, f, g, and h Studied by Semiempirical and Ab Initio MO/CI Methods
The semiempirical PM3 method has been used to calculate fully optimized structures of bacteriochlorophylls a, b, c, d, e, f, g, and h, magnesium−chlorin, and magnesium−bacteriochlorin. Several configuration interaction (CI) methods, the PM3 (5,5) CIS and CISD, ZINDO/S CIS (n,n) with 2 < n <30, and ab initio CIS (5,5)/6-31G* methods, were tested for their predictive power in estimation of spectroscopic properties of bacteriochlorophylls. The ZINDO/S CIS (15,15) method turned out the best results for overall simulation of absorption spectra. Both the transition energies and relative intensities of the Qy, Qx, and Soret bands were correctly predicted. The effect of solvent coordination on the …
Excitation Energy-Transfer in the LH2 Antenna of Photosynthetic Purple Bacteria via Excitonic B800 and B850 States
A newly developed CIEM method that uses a combination of semi-empirical or ab-initio configuration interaction methods and exciton theory to predict electronic energies, eigenstates, absorption and CD spectra of aggregated chromophoric systems with environmental interactions included is extended and used for estimation of excitation energy transfer rates. Excitonic energy levels of the two ring systems the B800 and the B850 of the light harvesting antenna LH2 of Rhodopseudomonas acidophila and the corresponding absorption spectrum were calculated by assuming inter-ring interactions to be zero. Excitation energy transfer rates were calculated by using the Fermi Golden rule with the dipole - …
Dielectric friction effects on rotational reorientation of three cyanine dyes in n-alcohol solutions
We have estimated the effect of dielectric friction on the rotational correlation times of three cationic cyanine dyes. Dielectric corrections were evaluated by using the Stokes–Einstein-Debye hydrodynamic continuum model including the dielectric friction for DiIC2, DiIC6, and DiIC14 in different n-alcohol solutions at room temperature. The dielectric corrections were done to cis and trans conformations of the cyanine dyes. For the trans conformations, which were found more stable than cis conformations, the dielectric model seemed to be more properly suited. The ground and excited state dipole moments for the calculations were evaluated from ab initio molecular orbital calculations and for…
Interactions between cationic amylose derivatives and a pulp fiber model surface studied by molecular modelling
This study was performed in order to obtain more information about the interactions between pulp fibers and acetylated cationic starch derivatives on a molecular scale. The adsorption of the polymers on the fiber surface was studied by simulating polymers on a fiber model surface at 300 K. Fractional atomic coordinates of regenerated cellulose II were used to generate a cellulose fiber surface model. Carboxylate groups were added on the cellulose surface to represent the anionic charge of pulp fiber which originates from hemicelluloses. Amylose chains cationized and acetylated atom by atom were chosen to represent four different starch derivatives. Atomic charges used in simulations were ca…
Quantum chemical simulation of excited states of chlorophylls, bacteriochlorophylls and their complexes
The present review describes the use of quantum chemical methods in estimation of structures and electronic transition energies of photosynthetic pigments in vacuum, in solution and imbedded in proteins. Monomeric Mg-porphyrins, chlorophylls and bacteriochlorophylls and their solvent 1:1 and 1:2 complexes were studied. Calculations were performed for Mg-porphyrin, Mg-chlorin, Mg-bacteriochlorin, mesochlorophyll a, chlorophylls a, b, c(1), c(2), c(3), d and bacteriochlorophylls a, b, c, d, e, f, g, h, plus several homologues. Geometries were optimised with PM3, PM3/CISD, PM5, ab initio HF (6-31G*/6-311G**) and density functional B3LYP (6-31G*/6-311G**) methods. Spectroscopic transition energ…
Semiempirical PM5 molecular orbital study on chlorophylls and bacteriochlorophylls: Comparison of semiempirical,ab initio, and density functional results
The semiempirical PM5 method has been used to calculate fully optimized structures of magnesium-bacteriochlorin, magnesium-chlorin, magnesium-porphin, mesochlorophyll a, chlorophylls a, b, c(1), c(2), c(3), and d, and bacteriochlorophylls a, b, c, d, e, f, g, and h with all homologous structures. Hartree-Fock/6-31G* ab initio and density functional B3LYP/6-31G* methods were used to optimize structures of methyl chlorophyllide a, chlorophyll c(1), and methyl bacteriochlorophyllides a and c for comparison. Spectroscopic transition energies of the chromophores and their 1:1 or 1:2 solvent complexes were calculated with the Zindo/S CIS method. The self-consistent reaction field model was used t…
Quantum Chemical Simulations of Excited-State Absorption Spectra of Photosynthetic Bacterial Reaction Center and Antenna Complexes
The semiempirical ZINDO/S CIS configuration interaction method has been used to study the ground- and excited-state absorption spectra of wild type and heterodimer M202HL reaction centers from purple bacterium Rhodobacter sphaeroides as well as of peripheral LH2 and LH3 light harvesting complexes from purple bacterium Rhodopseudomonas acidophila. The calculations well reproduce the experimentally observed excited-state absorption spectra between 1000 and 17,000 cm(-1), despite the necessarily limited number of chromophores and protein subunits involved in the calculations. The electron density analysis reveals that the charge transfer between adjacent chromophores dominates the excited-stat…
Supramolecular chirality and symmetry breaking of fluoride complexes of achiral foldamers
Aromatic oligoamide foldamers containing a central pyridine-2,6-dicarbonyl motif are partially preorganized to favor the binding of fluoride anions. In the solid state, the foldamer-fluoride complexes form achiral, polar and chiral crystal structures depending on the chemical structure of the foldamer. One of the six foldamers studied here, a C2v symmetrical foldamer (1), formed repeatedly chiral crystal structures when crystallized with tetra-butylammonium fluoride, showing supramolecular bulk chirality and symmetry breaking in crystallization.
Hexagonal Microparticles from Hierarchical Self-Organization of Chiral Trigonal Pd3L6 Macrotetracycles
Construction of structurally complex architectures using inherently chiral, asymmetric, or multi-heterotopic ligands is a major challenge in metallosupramolecular chemistry. Moreover, the hierarchical self-organization of such complexes is unique. Here, we introduce a water-soluble, facially amphiphilic, amphoteric, chiral, asymmetric, and hetero-tritopic ligand derived from natural bile acid, ursodeoxycholic acid. We show that via the supramolecular transmetalation reaction, using nitrates of Cu(II) or Fe(III), and subsequently Pd(II), a superchiral Pd3L6 complex can be obtained. Even though several possible constitutional isomers of Pd3L6 could be formed, because of the ligand asymmetry a…
Exciton interactions in self-organised bacteriochlorophyll a - aggregates
Exciton interactions of self-organised bacteriochlorophyll a - aggregates in non-polar solution linked via water and dioxane have been studied. Absorption and CD spectra of the aggregates show large red shifts typical of J-aggregates. Femtosecond excitation of the Qy band of the aggregates is followed by wavelength dependent non-exponential picosecond relaxation and anisotropy decay takes place in subpicosecond time scale. To explain these observations exciton theory and semi-empirical MO/CI calculations, that constitute the basis of the CIEM-approach developed by Linnanto et al. (J. Phys. Chem. B, 1999, 103B, 8739) was used. Structural models of aggregates were created by using the molecul…
A new potential toxaphene congener: synthesis, GC/EI-MS study, crystal structure, NMR analysis, and ab initio calculations of 3-endo,5-endo-dichloro-7,7-bis-chloromethyl-4-dichloromethyl-tricyclo[2.2.1.02,6]heptane
Abstract A new potential toxaphene congener 3- endo ,5- endo -dichloro-7,7-bis-chloromethyl-4-dichloromethyl-tricyclo[2.2.1.0 2,6 ]heptane 2 has been isolated from reaction mixture obtained by the chlorination of 2- exo ,10,10-trichlorobornane 1 . The X-ray structural analysis of 2 revealed an unusual tricyclic structure, where the two chlorine atoms occupying endo -positions are in close spatial proximity with each other and near to the neighbouring CHCl 2 group. Further, it revealed that the symmetry of the molecule is distorted. The 1 H and 13 C NMR spectra of 2 have been assigned by means of 1 H, 1 H d ouble- q uantum f iltered co rrelation s pectroscop y (DQF COSY), PFG 1 H, 13 C HMQC …
Theoretical study of excitation transfer from modified B800 rings of the LH II antenna complex of Rps. acidophila
The recently developed configuration interaction exciton model has been applied to study spectral shifts and B800 to B850 energy transfer rates in a series of modified LH2 light harvesting antenna complexes of the purple bacterium Rhodopseudomonas acidophila. Complexes, where the in vivo B800 bacteriochlorophyll a chromophores are exchanged with different tetrapyrroles including chlorophyll a were studied. Absorption spectra of the modified complexes were simulated by using quantum chemical methods to evaluate site and interaction energies and exciton theory to generate the eigenstates of the chromophore assemblies. Four experimental input parameters: the transition moment of Bchl a, the di…
Macrocycles prepared from lithocholic acid, piperazine and isomeric pyridine dicarboxylic acids and their selective affinities towards sodium and potassium
Abstract Two novel macrocycles prepared from lithocholic acid, piperazine and pyridine dicarboxylic acids (2,6- and 3,5-isomers), have been characterized by 13C NMR and ESI–MS techniques. In case of the pyridine-2,6-dicarboxylate derivative, the molecular formula of the cycle was C59H87O6N3 (I), while the pyridine-3,5-dicarboxylate derivative (II) was a trimeric structure by molecular mass when compared with I. Furthermore, cycle I showed a special affinity towards potassium cation, while II possessed significant proton and sodium cation recognition properties.
Excitation energy transfer in isolated chlorosomes from Chloroflexus aurantiacus
Abstract Chlorosomes from green photosynthetic bacteria Chloroflexus aurantiacus have been studied by time-resolved femtosecond transient absorption spectroscopy. The fastest kinetics of 200–300 fs resolved, was interpreted to stem for intra-chlorosomal excitation energy transfer. Energy transfer from the antenna to the baseplate appeared as a major 9.2 ps rise component detected at the baseplate probe wavelength. Excitation energy transfer rates were evaluated for a model chlorosome. Calculated rod to rod, and rods to baseplate rate constants of 200–400 fs and 10–20 ps, respectively, are in accord with the experimental results.
Molecular modeling studies of interactions between sodium polyacrylate polymer and calcite surface
Abstract The interactions between calcite pigment and sodium polyacrylate dispersing agent, widely used in papermaking as paper coating components, were investigated using classical force field and quantum chemical approaches. The objective was to understand interactions between the calcite surface and sodium polyacrylate polymer at 300 K using molecular dynamics simulations. A quantum mechanical ab initio Hartree–Fock method was also used to obtain detailed information about the sodium polyacrylate polymer structure. The effect of water molecules (moisture) on the interactions was also examined. Calculations showed that molecular weight, branching and the orientation of sodium polyacrylate…
Energy transfer in LH2 of Rhodospirillum Molischianum, studied by subpicosecond spectroscopy and configuration interaction exciton calculations.
Two color transient absorption measurements were performed on a LH2 complex from Rhodospirillum molischianum by using several excitation wavelengths (790, 800, 810, and 830 nm) and probing in the spectral region from 790 to 870 nm at room temperature. The observed energy transfer time of ∼1.0 ps from B800 to B850 at room temperature is longer than the corresponding rates in Rhodopseudomonas acidophila and Rhodobacter sphaeroides. We observed variations (0.9-1.2 ps) of B800-850 energy transfer times at different B800 excitation wavelengths, the fastest time (0.9 ps) was obtained with 800 nm excitation. At 830 nm excitation the energy transfer to the B850 ring takes place within 0.5 ps. The m…
Dimensionality Variation in Polymeric Metallo‐Organic Frameworks
Single crystal X-ray crystallography was used to determine the structures of four metallo-organic complexes derived from pyridyl ligands and the metal ions, Cu2+, Zn2+ and Ag+. Two metallo-organic layer framework structures (1 and 3), a strand (2) and a dimer (4) structure were formed when the tetradentate ligands, tetrakis(nicotinoxymethyl)methane (TNM) and tetrakis(isonicotinoxymethyl)methane (TINM), were reacted with the first and second row transition metal cations, copper, silver, and zinc. The choice of anion and ligand was found to affect the outcome of the structure. Contrary to our previous results with the same ligands and similar transition metal cations, no genuine 3D metallo-or…
Synthesis, characterization, and thermal behavior of steroidal dendrons
A series of novel dendritic steroidal polyesters of first and second generation has been synthesized in convergent fashion by the use of 2,2-bis(hydroxymethyl)propionic acid as a repeating unit. The first- and second-generation hydroxy-functionalized dendrons with a variety of surface modifications were produced through the use of four bile acids: lithocholic acid (LCA), ursodeoxycholic acid (UDCA), deoxycholic acid (DCA), and cholic acid (CA). The thermal behavior of the steroidal dendrons was characterized by differential scanning calorimetry (DSC) and by thermogravimetric analysis (TGA). Finally, quantum chemical calculation methods were used to study the geometries of the dendrons and t…
Exciton description of chlorosome to baseplate excitation energy transfer in filamentous anoxygenic phototrophs and green sulfur bacteria.
A description of intra-chlorosome and from chlorosome to baseplate excitation energy transfer in green sulfur bacteria and in filamentous anoxygenic phototrophs is presented. Various shapes and sizes, single and multiwalled tubes, cylindrical spirals and lamellae of the antenna elements mimicking pigment organization in chlorosomes were generated by using molecular mechanics calculations, and the absorption, LD, and CD spectra of these were predicted by using exciton theory. Calculated absorption and LD spectra were similar for all modeled antenna structures; on the contrary, CD spectra turned out to be sensitive to the size and pigment orientations in the antenna. It was observed that, bri…
Exciton Interactions and Femtosecond Relaxation in Chlorophyll a−Water and Chlorophyll a−Dioxane Aggregates
Chlorophyll a (Chl a) in hydrocarbon solution with a small amount of dioxane or water shows red-shifted absorption bands at 686 nm and at 700 nm (dioxane) and at 745 nm (water), indicative of self-organized aggregate structures in solution. To study the relationship between the structure and spectral properties of the aggregates, several one-dimensional model structures of Chl a−dioxane and Chl a−water aggregates were computed by the molecular mechanics method. Three overall structures ranging from stick to a ring shape were energetically favored for the dioxane system. All these structures contain structural heterogeneity that consists of repeating dimers that further form tetramer substru…
E-2-Benzylidenebenzocycloalkanones. IV. Studies on transmission of substituent effects on 13C NMR chemical shifts of E-2-(X-benzylidene)-1-tetralones, and -benzosuberones. Comparison with the 13C NMR data of chalcones and E-2-(X-benzylidene)-1-indanones
Abstract Single substituent parameter (SSP) and dual substituent parameter (DSP) analyses were applied to study the transmission of substituent effects on selected 13C NMR chemical shifts of the cyclic chalcone analogues, E-2-(4′-X-benzylidene)-1-tetralones (2) and E-2-(4′-X-benzylidene)-1-benzosuberones (3). In order to study how the geometry of the cyclic chalcone analogues affects the transmission of substituent effects similar investigations with the respective chalcones (4) were also performed. The results obtained earlier with the five-membered analogue E-2-(4′-X-benzylidene)-1-indanones (1) were also involved in the comparisons. Geometry optimization of the unsubstituted 1a, 2a, 3a a…
Supramolecular chirality in organogels: a detailed spectroscopic, morphological, and rheological investigation of gels (and xerogels) derived from alkyl pyrenyl urethanes.
This Article addresses the formation of chiral supramolecular structures in the organogels derived from chiral organogelator 1R (or 2R), and its mixtures with its enantiomer (1S) and achiral analogue 3 by extensive circular dichroism (CD) spectroscopic measurements. Morphological analysis by atomic force microscopy (AFM) and scanning electron microscopy (SEM) were complemented by the measurements of their bulk properties by thermal stability and rheological studies. Specific molecular recognition events (1/3 vs 2/3) and solvent effects (isooctane vs dodecane) were found to be critical in the formation of chiral aggregates. Theoretical studies were also carried out to understand the interact…
Chlorodicyclopentadienyloxoniobium(V) complexes revisited: The origin of the asymmetry in the 1H- and 13C-NMR spectra, X-ray crystal structures and ab initio/HF and DFT/B3LYP calculations
Abstract 1H- and 13C-NMR spectra of chlorodicyclopentadienyloxoniobium(V) complex I and its four 1,1′-dialkyl substituted derivatives II–V have been recorded and assigned based on DQF 1H,1H-COSY and PFG 1H,13C-HMQC and HMBC experiments. Non-equivalences of all cyclopentadienyl protons and carbons in II–V (as reflected by their different 1H- and 13C-NMR chemical shifts) are explained by synchronous and out-of-phase rotations of the substituted cyclopentadienyl rings. A non-equivalence of the methyls in III (1,1′-di-isopropyl) is explained by a detailed inspection of the rotamers of the isopropyl groups. The X-ray structural data show that III and IV (1-methyl-1′-tert-butyl) crystallize in th…
Electronic States, Absorption Spectrum and Circular Dichroism Spectrum of the Photosynthetic Bacterial LH2 Antenna of Rhodopseudomonas acidophila as Predicted by Exciton Theory and Semiempirical Calculations
A new approach that uses a combination of semiempirical configuration interaction method and exciton theory to calculate electronic energies, eigenstates, absorption spectrum and circular dichroism (CD) spectrum of the LH2 antenna of Rhodopseudomonas acidophila is introduced. A statistical simulation that uses experimental homogeneous line widths was used to account for the inhomogeneous line width of the observed spectrum. Including the effect of orbital overlap of the close-lying pigments of the B850 ring and the effect of the pigment protein interaction in the B800 ring allowed a successful simulation of the experimental absorption and CD spectra of the antenna at room temperature. Two e…
Molecular modeling studies of interactions between styrene–butadiene latex and sodium polyacrylate polymer surface
Abstract The interaction between two important paper coating ingredients, sodium polyacrylate polymer dispersing agent and styrene–butadiene latex binder, was studied using classical force field and quantum chemical methods. The objective was to understand the adsorption of styrene–butadiene latex on the sodium polyacrylate polymer model surfaces at 300 K using molecular dynamics simulations. A quantum mechanical ab initio Hartree–Fock method was also used to obtain detailed information about the above interactions. In addition, the effect of moisture was investigated. Calculations showed that the conformation and orientation of styrene–butadiene latex, the number of carboxylate groups in t…
3α,3′α-Bis(n-acetoxyphenylcarboxy)-5β-cholan-24-oic acid ethane-1,2-diol diesters (n = 2-4):13C NMR chemical shifts, variable-temperature and NOE1H NMR measurements and MO calculations of novel bile acid-based dimers
Three novel bile acid-based molecular dimers, 3α,3′α-bis(n-acetoxyphenylcarboxy)-5β-cholan-24-oic acid ethane-1,2-diol diesters (n = 2–4), 1–3, were synthesized from lithocholic acid (3α-hydroxy-5β-cholan-24-oic acid) ethane-1,2-diol diester and isomeric n-acetoxybenzoyl chlorides (n = 2–4). Their cleft type conformational preferences were suggested theoretically by PM3 molecular orbital calculations. Molecular weights determined by the matrix-assisted laser desorption/ionization time-of-flight technique and 13C NMR chemical shifts of the 1–3 are also presented. Copyright © 2000 John Wiley & Sons, Ltd.
Structural and Spectroscopic Properties of Mg−Bacteriochlorin and Methyl Bacteriochlorophyllidesa,b,g, andhStudied by Semiempirical, ab Initio, and Density Functional Molecular Orbital Methods
Ab initio HF/6-31G* and density functional B3LYP/6-31G* methods have been used to calculate fully optimized structures of methyl bacteriochlorophyllides a, b, g, and h and magnesium-bacteriochlorin...
Modelling excitonic energy transfer in the photosynthetic unit of purple bacteria
Abstract Molecular mechanics and quantum chemical configuration interaction calculations in combination with exciton theory were used to predict vibronic energies and eigenstates of light harvesting antennae and the reaction centre and to evaluate excitation energy transfer rates in the photosynthetic unit of purple bacteria. Excitation energy transfer rates were calculated by using the transition matrix formalism and exciton basis sets of the interacting antenna systems. Energy transfer rates of 600–800 fs from B800 ring to B850 ring in the LH2 antenna, 3–10 ps from LH2 to LH2 antenna, 2–8 ps from LH2 to LH1 antenna and finally 30–70 ps from LH1 to the reaction centre were obtained. Depend…
CCDC 1552171: Experimental Crystal Structure Determination
Related Article: Kaisa Helttunen, Riia Annala, Aku Suhonen, Elisa Nauha, Juha Linnanto, Maija Nissinen|2017|CrystEngComm|19|5184|doi:10.1039/C7CE01109A
CCDC 1552172: Experimental Crystal Structure Determination
Related Article: Kaisa Helttunen, Riia Annala, Aku Suhonen, Elisa Nauha, Juha Linnanto, Maija Nissinen|2017|CrystEngComm|19|5184|doi:10.1039/C7CE01109A
CCDC 1552170: Experimental Crystal Structure Determination
Related Article: Kaisa Helttunen, Riia Annala, Aku Suhonen, Elisa Nauha, Juha Linnanto, Maija Nissinen|2017|CrystEngComm|19|5184|doi:10.1039/C7CE01109A
CCDC 1552175: Experimental Crystal Structure Determination
Related Article: Kaisa Helttunen, Riia Annala, Aku Suhonen, Elisa Nauha, Juha Linnanto, Maija Nissinen|2017|CrystEngComm|19|5184|doi:10.1039/C7CE01109A
CCDC 1552173: Experimental Crystal Structure Determination
Related Article: Kaisa Helttunen, Riia Annala, Aku Suhonen, Elisa Nauha, Juha Linnanto, Maija Nissinen|2017|CrystEngComm|19|5184|doi:10.1039/C7CE01109A
CCDC 1552174: Experimental Crystal Structure Determination
Related Article: Kaisa Helttunen, Riia Annala, Aku Suhonen, Elisa Nauha, Juha Linnanto, Maija Nissinen|2017|CrystEngComm|19|5184|doi:10.1039/C7CE01109A
CCDC 1552169: Experimental Crystal Structure Determination
Related Article: Kaisa Helttunen, Riia Annala, Aku Suhonen, Elisa Nauha, Juha Linnanto, Maija Nissinen|2017|CrystEngComm|19|5184|doi:10.1039/C7CE01109A
CCDC 1552176: Experimental Crystal Structure Determination
Related Article: Kaisa Helttunen, Riia Annala, Aku Suhonen, Elisa Nauha, Juha Linnanto, Maija Nissinen|2017|CrystEngComm|19|5184|doi:10.1039/C7CE01109A