C − H···π interactions in the metal-porphyrin complexes with chelate ring as the h acceptor

Specific C − H···π interactions with the π-system of porphyrinato chelate ring were found in crystal structures of transition metal complexes from the CSD and statistical analysis of geometrical parameters for intramolecular and intermolecular interactions was done. DFT calculations on a model system show that energy of the interaction is 1.58 kcal/mol and that the strongest interaction occurs when the distance between hydrogen atom and the center of the chelate ring is 2.6 Å. This prediction is in good agreement with the distances for intermolecular interactions found in the crystal structures. In many cases the intramolecular interaction distances are much shorter than 2.6 Å, and these short distances appear to be caused by geometrical constrains. The C − H···π interactions with chelate ring of porphyrinato ligand can be important in biomolecules with porphyrin as they can influence the structure, contribute to the stability and play some role in function of biomolecules.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

'Tipovi' aromatičnosti

The field of aromaticity continues to be controversial. The central theme of this controversy is the definition of aromaticity itself. Today, the proliferation of 'types' of aromaticity goes far beyond the conventional confines and has been extended to include heterosystems, chelate metallacycles in which metalloaromaticity stabilizes coordinated chelate ligands, inorganic molecules, and transition metal oxides. A considerable number of prefixes joined to the term of aromaticity (anti-, non-, homo-, quasi-, pseudo-, etc.) and other 'types' of aromaticity suggested so far, such as classical aromaticity, magnetic aromaticity, Mõbius aromaticity, σ-aromaticity, local-aromaticity, 3D-aromaticity and spherical aromaticity pose additional problems. All these terms related to specific properties of the molecular system illustrate that aromaticity should take into consideration multiple structural, chemical and physical manifestations - it must be a multi-dimensional phenomenon. In the following we will briefly outline the various 'types' of aromaticity for the reader, to get insight into the complexity of the vexing and nebulous concept of aromaticity.U prethodnom broju smo već rekli da je još od Majerovog (Meyer) otkrića tiofena, koji je veoma sličan benzenu po fizičkim i hemijskim osobinama, postalo jasno da je pojam aromatičnosti mnogo širi od hemije benzena i njegovih jedinjenja. Danas postoji mnogo 'tipova' aromatičnosti, a samom pojmu aromatičnosti su dodati razni prefiksi (anti-, non-, homo-, pseudo-, kvazi-, super-, itd.). Svi ovi tipovi aromatičnosti ukazuju da se koncept aromatičnosti sastoji od mnogobrojnih strukturnih, hemijskih i fizičkih manifestacija, tj. da je aromatičnost jedan multidimenzioni fenomen. U ovom članku biće predstavljeni neki od najrasprostranjenijih tipova aromatičnosti

Study of C−H⋅⋅⋅π interactions with pyrrole and chelate rings in metal-porphyrin complexes

The Cambridge Structural Database (CSD) was screened in order to find and investigate specific C−H⋅⋅⋅π interactions between C−H groups and two types of rings with delocalized π-bonds that exist in porphyrin: pyrrole and six-membered chelate. Statistical analysis of geometrical parameters for interactions in both types of rings was done. In order to determine preferred positions in porphyrinato ring for C−H⋅⋅⋅π interactions fifteen different points distributed over porphyrin ring have been chosen and each of them have been analyzed. Calculations of these interactions by density functional theory (DFT) have been done on three different model systems.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Kratka istorija pojma aromatičnosti

One of the most used concepts in modern chemical literature is concept of aromaticity. However, aromaticity, similar to some other very useful chemical concepts, cannot be quantified and directly measured. Hence, aromaticy is more abstract concept than observable. With the time, concept of aromaticity has evolved. Nowadays, aromaticity is connected with the delocalization of the electrons in rings, and from it emerged magnetic properties of the systems, that are considered as very important

Određena je struktura i otkriven mehanizam selektivnosti kalijumovog kanala

Potassium Channels play a central role in the function of nearly every living cell. In the nervous system they govern the frequency of nerve impulses. The Potassium Channels are highly selective-perhaps as much as 10000:1 for K+ over Na+, despite the minimal structural difference between the two. At the same time, Potassium channels promote tremendous ion flux; in some cases on the order of 108 ions per second pass through a single open channel. In little more than a decade, we have come from almost complete ignorance about the molecular nature of Potassium channels to a high-resolution structure and mechanism for its selectivity

'Tipovi' aromatičnosti

The field of aromaticity continues to be controversial. The central theme of this controversy is the definition of aromaticity itself. Today, the proliferation of 'types' of aromaticity goes far beyond the conventional confines and has been extended to include heterosystems, chelate metallacycles in which metalloaromaticity stabilizes coordinated chelate ligands, inorganic molecules, and transition metal oxides. A considerable number of prefixes joined to the term of aromaticity (anti-, non-, homo-, quasi-, pseudo-, etc.) and other 'types' of aromaticity suggested so far, such as classical aromaticity, magnetic aromaticity, Mõbius aromaticity, σ-aromaticity, local-aromaticity, 3D-aromaticity and spherical aromaticity pose additional problems. All these terms related to specific properties of the molecular system illustrate that aromaticity should take into consideration multiple structural, chemical and physical manifestations - it must be a multi-dimensional phenomenon. In the following we will briefly outline the various 'types' of aromaticity for the reader, to get insight into the complexity of the vexing and nebulous concept of aromaticity.U prethodnom broju smo već rekli da je još od Majerovog (Meyer) otkrića tiofena, koji je veoma sličan benzenu po fizičkim i hemijskim osobinama, postalo jasno da je pojam aromatičnosti mnogo širi od hemije benzena i njegovih jedinjenja. Danas postoji mnogo 'tipova' aromatičnosti, a samom pojmu aromatičnosti su dodati razni prefiksi (anti-, non-, homo-, pseudo-, kvazi-, super-, itd.). Svi ovi tipovi aromatičnosti ukazuju da se koncept aromatičnosti sastoji od mnogobrojnih strukturnih, hemijskih i fizičkih manifestacija, tj. da je aromatičnost jedan multidimenzioni fenomen. U ovom članku biće predstavljeni neki od najrasprostranjenijih tipova aromatičnosti

Kriterijumi za karakterizaciju aromatičnosti

Because of the importance of aromaticity in chemistry, there have been many attempts to rationalize and quantify this property, and to derive a universal quantitative measure of it. However, because of its multiple manifestations, there is not yet any generally accepted single quantitative definition of aromaticity. The evaluation of aromaticity is usually based on the classical aromaticity criteria, which can roughly be divided into six categories: electronic, energetic, structural or geometrical, magnetic, reactivity-based measures and spectroscopic criteria. Which criteria one chooses the best and the relationship between these different criteria (i.e., their orthogonality or nonorthogonality) is still a matter of debate

Intramolecular C-H⋯π interactions in metal-porphyrin complexes

Cambridge Structural Database (CSD) was screened in order to find intramolecular C-H⋯π interactions with a chelate ring of coordinated porphyrin. It was found 154 crystal structures with 244 intramolecular C-H⋯π interactions in transition metal complexes with derivatives of porphyrin. Comparison of interacting distances indicates that interactions of hydrogen atoms in positions 2 and 6 of axially coordinated pyridine are more favorable with ruffled than with planar porphyrin

Supplementary data for the article: Antonijević, I. S.; Janjić, G. V.; Milčić, M. K.; Zarić, S. D. Preferred Geometries and Energies of Sulfur-Sulfur Interactions in Crystal Structures. Crystal Growth and Design 2016, 16 (2), 632–639. https://doi.org/10.1021/acs.cgd.5b01058

Supplementary material for: [https://doi.org/10.1021/acs.cgd.5b01058]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2042]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3596

Katjon-¶ interakcije

The Cation-¶ interaction is recognized as an important noncovalent bonding force in a wide range of molecular systems. The gas-phase studies of ion-molecule complexes established that Cation-¶ bind strongly to simple aromatic systems. High-level theoretical studies of ion-molecule systems have shown excellent agreement between calculated and experimental bonding energies. It has been documented that Cation-¶ interactions are important for molecular recognition in many biological systems. Investigations of Cation-¶ interactions in proteins and peptides show that Cation-¶ interaction pairs contribute at least as much to protein stability and the structural motifs of native protein as more conventional interactions. Interactions of cationic metal complexes with ¶ systems had been observed and investigated.Katjon-¶ interakcije predstavljaju veoma važan tip nekovalentnih veza u mnogim molekulskim sistemima i važne su za molekulska prepoznavanja u mnogim biološkim sistemima. Gasno-fazna ispitivanja jonsko-molekulskih kompleksa pokazala su da se katjoni vezuju za jednostavne aromatične sisteme velikom jačinom. Smatra se da katjon-¶ interakcije sa proteinima i peptidima podjednako doprinose stabilnosti proteina kao i strukturni motivi nativnih proteina. U ovom radu dat je pregled interakcija katjonskih kompleksa metala sa ¶ sistemima