Chemistry Commons^™

Design, Synthesis, Characterization, And Application Of Peptides As Different Medical Treatment, Krystal Renee Fontenot

LSU Doctoral Dissertations

A peptide is defined, as a molecule that contains less than fifty amino acids; anything larger is a protein. Peptides are important molecules because they have diverse uses. Peptides were utilized in two ways: 1) Peptide bioconjugates containing a fluorescent porphyrin or phthalocyanine macrocycle were designed and investigated, with or without a PEG moiety for selective targeting of the epidermal growth factor receptor (EGFR). 2) Amyloid aggregating mitigating peptides (AAMPs) was synthesized and investigated containing polar amino acids, MiniPEGs, and/or ααAAs that have the ability to inhibit and disrupt Amyloid Beta (Aβ). The peptide bioconjugates containing a porphyrin or phthalocyanine …

Features For Non-Targeted Cross-Sample Analysis With Comprehensive Two-Dimensional Chromatography, Stephen E. Reichenbach, Xue Tian, Chiara Cordero, Qingping Tao

School of Computing: Faculty Publications

This review surveys different approaches for generating features from comprehensive two-dimensional chromatography for non-targeted cross-sample analysis. The goal of non-targeted cross-sample analysis is to discover relevant chemical characteristics (such as compositional similarities or differences) from multiple samples. In non-targeted analysis, the relevant characteristics are unknown, so individual features for all chemical constituents should be analyzed, not just those for targeted or selected analytes. Cross-sample analysis requires matching the corresponding features that characterize each constituent across multiple samples so that relevant characteristics or patterns can be recognized. Non-targeted, cross-sample analysis requires generating and matching all features across all samples. Applications of …

Quantitative Analysis Of Some Important Metals And Metalloids In Tobacco Products By Inductively Coupled Plasma-Mass Spectrometry (Icp-Ms), Syed Ghulam Musharraf, Muhammad Shoaib, Amna Jabbar Siddiqui, Muhammad Najam-Ul-Haq, Aftab Ahmed

Pharmacy Faculty Articles and Research

Background: Large scale usage of tobacco causes a lot of health troubles in human. Various formulations of tobacco are extensively used by the people particularly in developing world. Besides several toxic tobacco constituents some metals and metalloids are also believed to pose health risks. This paper describes inductively coupled plasma-mass spectrometric (ICP-MS) quantification of some important metals and metalloids in various brands of smoked, sniffed, dipped and chewed tobacco products.

Results: A microwave-assisted digestion method was used for sample preparation. The method was validated by analyzing a certified reference material. Percentage relative standard deviation (% R.S.D.) between recovered …

A New, Simple, Green And One-Pot Four-Component Synthesis Of Bare And Poly(Α, Γ, L-Glutamic Acid) Capped Silver Nanoparticles, Magdalena Stevanović, Igor Savanović, Vuk Uskoković, Srečo D. Škapin, Ines Bračko, Uroš Jovanović, Dragan Uskoković

Pharmacy Faculty Articles and Research

A simple and green chemical method has been developed to synthesize stable bare and capped silver nanoparticles based on the reduction of silver ions by glucose and capping by poly(α,γ,Lglutamic acid) (PGA). The use of ammonia during synthesis was avoided. PGA has had a dual role in the synthesis and was used as a capping agent to make the silver nanoparticle more biocompatible and to protect the nanoparticles from agglomerating in the liquid medium. The synthesized PGA-capped silver nanoparticles in the size range 5–45 nm were stable over long periods of time, without signs of precipitation. Morphological examination has shown …

A Greener Synthesis Of 2-Aminochromenes In Ionic Liquid And Evaluation Of Their Antiproliferative Activities, M. Sudershan Rao, Bhupender S. Chhikara, Rakesh Tiwari, Amir Nasrolahi Shirazi, Keykavous Parang, Anil Kumar

Pharmacy Faculty Articles and Research

An improved simple and facile synthesis of chromene derivatives by employing threecomponent one-pot condensation reaction of β-naphthol, aromatic aldehydes, and malononitrile in ionic liquids is described.

Mining Functional Subgraphs From Cancer Protein-Protein Interaction Networks, Ru Shen, Nalin Goonesekere, Chittibabu Guda

Faculty Work

Background: Protein-protein interaction (PPI) networks carry vital information about proteins’ functions. Analysis of PPI networks associated with specific disease systems including cancer helps us in the understanding of the complex biology of diseases. Specifically, identification of similar and frequently occurring patterns (network motifs) across PPI networks will provide useful clues to better understand the biology of the diseases.

Results: In this study, we developed a novel pattern-mining algorithm that detects cancer associated functional subgraphs occurring in multiple cancer PPI networks. We constructed nine cancer PPI networks using differentially expressed genes from the Oncomine dataset. From these networks we …

Kinetic Studies On Lactonization Of Quinone Propionic Acid Derivatives For The Development Of Redox Responsive Liposomes, K. L. Iresha Sampathi Perera

LSU Master's Theses

ABSTRACT Stimuli-responsive liposome systems that utilize endogenous triggers of tumor microenvironment have generated great attention in recent drug delivery research. Among such formulations, redox-responsive liposomes seem highly promising for cancer treatment due to their potential to release high drug concentrations upon reduction (by reductase enzymes). The research described in this thesis involved the evaluation of kinetics of trimethyl-lock quinone propionic acid reduction and lactonization, which accounts for payload release from trimethyl-lock quinone propionic acid-decorated liposomes. To achieve the ultimate goal of this research, several trimethyl-lock quinone propionic acid-based amide compounds were synthesized and characterized. Kinetic studies were carried out with …

Synthesis Of Fluorescent Poly(Styrene Sulfonate), Wayne Alfred Huberty

LSU Master's Theses

In 1978, Lee found an increase and then a large decrease in the diffusion coefficient of poly(lysine) as the concentration of salt is decreased (Lin, S. C.; Lee, W. I.; Schurr, J. M. Biopolymers 1978, 17, (4), 1041-1064). Since the “slow mode” discovery, many have studied it without finding a fully satisfactory answer. Additional dynamic light scattering (DLS) measurements have been the main experimental technique used for reinvestigating the slow mode decay. Although DLS is a powerful characterization tool, it depends on thermodynamic interactions. As complicated as they can be, thermodynamic interactions are much worse for polyelectrolytes because of the …

Your Body Is A Temple: Type-2 Diabetes In Mississippi And The Potential Role Of The Black Church In Diabetes Education And Intervention, Jonathon Troy Jackson

Honors Theses

Type-2 diabetes and obesity are two major health complications that are affecting many Mississippians, namely the African American population. A substantial amount of research has been conducted that explains the high prevalence rate of type-2 diabetes and obesity in the African American community as partially due to many secondary factors, including the Southern cuisine, food scarcity, physical inactivity, and poverty. Recently, efforts to reach the African American population about diabetes education and prevention in other Southern states have been directed to faith-based organizations. Researchers have hoped that faith-based intervention might be better suited at helping a wider audience in a …

Hydrothermal Synthesis And Characterization Of Nanosized Transition Metal Chromite Spinels, Shahid Khan Durrani, Syed Zahid Hussain, Khalid Saeed, Yaqoob Khan, Mohammad Arif, Nisar Ahmed

Turkish Journal of Chemistry

Homogeneous crystalline transition metal chromite spinels (MCr_2O_4, where M = Co, Mn, and Ni) were prepared by hydrothermal reaction of aqueous solutions containing the respective metal nitrate, chromium(III) nitrate, and sodium hydroxide in stoichiometric amounts at 180-200 °C and pH 10.5-11.5 for 11-13 h. The crystalline structure, microstructure, and thermal stability of the synthesized chromite products were analyzed by X-ray diffraction (XRD), scanning electron microscopy, thermogravimetry, and differential thermal analysis. The analysis results revealed that the CoCr_2O_4 and MnCr_2O_4 crystalline phases were thermally stable in the range of 750-800 °C. UV-visible studies showed that higher characteristic bands corresponded to the …

Microwave-Assisted Synthesis, Spectroscopy, And Crystal Structures Of [(H_2-(4,4'-Bipy)]^{2+} [Cr_2o_7]^{2-} And One-Dimensional Polymeric {[Mn(4,4'-Bipy)(Cr_2o_7)(H_2o)_2]\}_N Compounds, Hirihattaya Phetmung, Munee Wateh, Chaveng Pakawatchai

Turkish Journal of Chemistry

A compound (1), [H_2-(4,4'-bipy)]^{2+}[(Cr_2O_7)]^{2-} and a metal organic-inorganic coordination framework (2), [Mn(4,4'-bipy)(Cr_2O_77)(H_2O)_2] (4,4'-bipy=4,4' -bipyridine) were successfully synthesized by microwave method. Their characterization was performed by single crystal X-ray crystallography and FT-IR spectroscopy. The crystal structure of 1 revealed a diprotonated 4,4'-bipyridium dichromate compound while compound 2 is an onedimensional (1D) polymer in which (Cr_2O_7)^{2-} acts as a bridging ligand supporting the formation of infinite {[Mn(4,4'-bipy)(Cr_2O_7)(H_2O)_2]}_n polymeric chains. The geometry of the 4,4'-bipy ring in 1 is typical coplanar, but twists in 2. In the free molecule 1, dichromate ligand adopts an eclipsed conformation, but adopts a staggered conformation in complex. …

Synthesis, Structural Characterization, And Benzyl Alcohol Oxidation Activity Of Mononuclear Manganese(Ii) Complex With 2,2'-Bipyridine: [Mn(Bipy)_2(Clo_4)_2], İbrahi̇m Kani̇, Mehmet Kurtça

Turkish Journal of Chemistry

A manganese(II) complex of 2,2'-bipyridine (bipy) was synthesized and characterized by X-ray diffraction, IR, and UV-vis spectroscopy. The activity of the complex was tested for oxidation of benzyl alcohols using t-BuOOH as an oxidant in organic solvents and in an organic/water biphasic system (hexane/H_2O, toluene/H_2O). The effect of solvent, temperature, oxidant, and some additives (KBr, N(C_4H_9)Br, and N-bromosuccinimide) on the oxidation of benzyl alcohol is reported. The results show that benzyl alcohol was selectively converted to benzaldehyde in 71.9% yield within 4 h in acetonitrile. Control experiments performed without catalyst and the corresponding metal salt as catalyst produced no benzaldehyde …

Capturing Motion, Allison Marsh

Section 3: Imaging the Fast Moving

No abstract provided.

Images From The Exhibit, Page 2, Allison Marsh

Handouts

No abstract provided.

Nucleic-Acid Based Lateral Flow Strip Biosensor Via Competitive Binding For Possible Dengue Detection, Erwin P. Enriquez, Henson L. Lee Yu, Christine Marie Montesa, Nina Rosario L. Rojas

Chemistry Faculty Publications

A low-cost, simple, rapid and selective nucleic-acid based lateral flow strip biosensor (LFSB) for possible dengue viral RNA detection is described in this study. The detection is based on competitive binding, where gold nanoparticles (AuNPs), with average size of ~10 nm confirmed using UV-Vis, TEM and AFM images, are used as visualizing agents. These are bioconjugated with DNA which competitively binds with its complementary strand either in the sample or in the test line of the LFSB. The detection scheme reduces the number of probes which effectively lowers the cost for the design of the test strip. The whole test …

Synthesis And Chemical Transformations Of Azonine Derivatives, Ahmed A. Fadda, Elsayed M. Afsah, Samir Bondock, Mohamed M. Hammouda

Turkish Journal of Chemistry

No abstract provided.

Synthesis And Structural And Electrochemical Characterization Of Novel Macrocyclic Vic-Dioxime Ligand And Its Mononuclear Transition And Nontransition Metal Complexes, Pervi̇n Deveci̇, Bi̇lge Taner, Zeynel Kiliç, Ali̇ Osman Solak, Emi̇ne Özcan

Turkish Journal of Chemistry

The reaction of N-(4-aminophenyl)aza-15-crown-5 (1) with anti-chlorophenylglyoxime (2) produces a novel azacrown ether containing vic-dioxime, N-(4-aminophenyl)aza-15-crown-5-phenylglyoxime (LH_2). LH_2 reacts with Ni(II), Cu(II), Co(II), Cd(II), and Zn(II) ions to yield the mononuclear transition and nontransition metal complexes [M(LH)_2] (M = Ni and Cu), [M(LH)_2(H_2O)_2] (M = Co), and [M(LH)(H_2O)(Cl)] (M = Cd and Zn). The structural features of LH_2 were studied using several techniques including elemental analysis, Fourier transform infrared spectroscopy (FT-IR), ultraviolet visible (UV-Vis), mass spectrometry (MS), 1-dimensional (1D) ^1H-NMR and ^{13}CNMR, distortionless enhancement by polarization transfer (DEPT) 2-dimensional (2D) heteronuclear single-quantum coherence (HSQC), and heteronuclear multiple-bond correlation (HMBC) techniques. …

Solvent-Free Michael Addition Of 2-Cyclohexenone Under Ultrasonic Irradiation In The Presence Of Long Chain Dicationic Ammonium Salts, Aytek Öge, Murat Emrah Mavi̇ş, Çi̇ğdem Yolaçan, Feray Aydoğan

Turkish Journal of Chemistry

Long chain dicationic ammonium salts (1a-1c), easily prepared from tert-amines and dihaloalkanes, were successfully used as efficient phase-transfer catalysts in the Michael addition reaction of various active methylene compounds to 2-cyclohexenone without solvent under ultrasonic irradiation. The investigated dicationic salts were more effective than monocationic tetrabutylammonium bromide, with short reaction times and high yields. This methodology was established under phase-transfer catalytic conditions and ultrasonic effects with many advantages, including the easy and cost-effective synthesis of the catalyst, mild reaction conditions, short reaction times, good yields, simple work-up procedures, and environmental friendliness.

Surfactant-Sensitized Spectrophotometric Determination Of Hg(Ii) In Water Samples Using 2-(2-Thiazolylazo)- P-Cresol As Ligand And Cetylpyridinium Chloride As Cationic Surfactant, Ramazan Gürkan, Tuğba Çepken, Hali̇l İbrahi̇m Ulusoy

Turkish Journal of Chemistry

A new, reliable, surfactant-sensitized method is described for the spectrophotometric determination of total and dissolved inorganic mercury at trace levels. The method is based on the ternary complex formation of Hg(II) with 2-(2-thiazolylazo)-p-cresol and a cationic surfactant, cetylpyridinium chloride, at pH 9.5. The detection and quantification limits of the method with surfactant were 6 and 19 \mu g L^{-1}, while those of the method without surfactant were 22 and 67 \mu g L^{-1}, respectively. The method obeys Beer's law at up to approximately 10 mg L^{-1} Hg(II) in an aqueous surfactant medium. The relative errors and relative standard deviations of …

One-Pot Synthesis Of Fully Substituted 1,3,4-Oxadiazole Derivatives From Aromatic Carboxylic Acids, Cyclobutanone And N-Isocyaniminotriphenylphosphorane, Mohsen Valizadeh Holagh, Abel Mohammadali Oglu Maharramv, Mirza Aliakbar Oglu Allahverdiyev, Ali Ramazani, Yavar Ahmadi, Ali Souldozi

Turkish Journal of Chemistry

Reactions of N-isocyaniminotriphenylphosphorane with cyclobutanone in the presence of aromatic (or heteroaromatic) carboxylic acids proceeded smoothly at room temperature and in neutral conditions to afford sterically congested 1-(5-aryl-1,3,4-oxadiazol-2-yl)- 1-cyclobutanol derivatives in high yields. The reaction proceeded smoothly and cleanly under mild conditions and no side reactions were observed. The structures of the products were deduced from their IR, ^1HNMR, and ^{13}CNMR spectra, and mass spectrometry.

Synthesis, Characterization, And Microwave-Promoted Catalytic Activity Of Novel Benzimidazole Salts Bearing Silicon-Containing Substituents In Heck-Mizoroki And Suzuki-Miyaura Cross-Coupling Reactions Under Aerobic Conditions, Hasan Küçükbay, Ni̇hat Şi̇reci̇, Ülkü Yilmaz, Selma Deni̇z, Mehmet Akkurt, Zeli̇ha Baktir, Orhan Büyükgüngör

Turkish Journal of Chemistry

A number of benzimidazole derivatives (1-8) were synthesized and the catalytic activity of these compounds in a catalytic system including Pd(OAc)_2 and K_2CO_3 in DMF-H_2O was evaluated in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions of aryl iodides, bromides, and chlorides with styrene and arylboronic acids under microwave irradiation and aerobic conditions. The yields of both the Heck-Mizoroki and the Suzuki-Miyaura cross coupling reactions with aryl iodides and aryl bromides were nearly quantitative. The synthesized 1-substituted benzimidazole (1) and benzimidazole salts (2-8) were identified by ^1H- and ^{13}C-NMR and IR spectroscopic methods, and micro analysis. The molecular structure of 7 was also …

Determination Of Cadmium In High Salt Content Matrices By Flow Injection Cold Vapor Atomic Absorption Spectrometry, Orkun Alp, Hakan Demi̇röz, Osman Yavuz Ataman, Nusret Ertaş

Turkish Journal of Chemistry

Flow injection cold vapor atomic absorption spectrometry (FI-CVAAS) was used for determination of cadmium in high salt matrices such as dialysis concentrates and textile leach solutions. The parameters such as acidity, concentration of reducing agent, reaction coil length, and carrier gas flow rate were investigated to obtain the best sensitivity. No significant background signal was observed even at high salt concentrations. Under the optimized conditions the limit of detection value (3s_b m^{-1}, where s_b is the standard deviation of the blank signals and m is the slope of the calibration graph) was found to be 0.05 ng mL^{-1} for an …

Synthesis And Evaluation Of Enzyme Inhibitory Potential Of Some Derivatives Of Scopolamine, Durre Shahwar, Muhammad Asam Raza, Tania Khan

Turkish Journal of Chemistry

This study was designed to synthesize and evaluate derivatives of scopolamine (1) as acetylcholine esterase and protease inhibitors. Scopolamine (1) was extracted from the aerial parts of Datura innoxia through bioassay guided fractionation. Five different derivatives of scopolamine (1) were synthesized, and identified through spectroscopic studies. Their acetylcholine esterase (AChE) and trypsin inhibitory potentials were determined through standard protocols and evaluated from the perspective of structure-activity relationship. The synthesized scopolamine derivatives (2-6) showed remarkable AChE inhibitory activity, except for scopoline (6). The results showed higher enzyme inhibition potential of the synthesized compounds (2-5) as compared to scopolamine (1). Maximum inhibition …

^{99m}Tc Labeled Levofloxacin As An Infection Imaging Agent: A Novel Method For Labeling Levofloxacin Using Cysteine\Cdot Hcl As Co-Ligand And In Vivo Study, Syed Ali Raza Naqvi, Malik Muhammad Ishfaq, Zulfiqar Ali Khan, Saeed Ahmad Nagra, Iftikhar Hussain Bukhari, Abdullah Ijaz Hussain, Nasir Mahmood, Sohail Anjum Shahzad, Asma Haque, Tanveer Hussain Bokhari

Turkish Journal of Chemistry

Levofloxacin was labeled with ^{99m}Tc using cysteine\cdot HCl as co-ligand and SnCl_2.2H_2O as reducing agent. The influence of various parameters such as amount of cysteine\cdot HCl, reducing agent, pH value, and reaction time on labeling process was studied. After optimizing the conditions the labeling was performed at pH 5 using 1 mg of levofloxacin, 500 \mu g of cysteine\cdot HCl, 50 \mu g of SnCl_2.2H_2O, and 15 min reaction time. The radiochemical purity was determined with the help of instant thin layer chromatography (ITLC) and reverse phase high performance liquid chromatography (RP-HPLC) which was more than 95% and was stable …

Synthesis Of Some New Urea And Thiourea Derivatives And Evaluation Of Their Antimicrobial Activities, Yildiz Gülkok, Tuba Bi̇çer, Fatma Kaynak Onurdağ, Selda Özgen, Mustafa Fethi̇ Şahi̇n, Deni̇z Songül Doğruer

Turkish Journal of Chemistry

In the present study, 18 new compounds were synthesized, 9 of which were urea (9a-e, 10a-d) while the others were thiourea (11a-e, 12a-d) derivatives. These derivatives were prepared by the reaction of 6-amino-5-nonsubstituted/chloro-3-methyl-2(3H)- benzoxazolones used as key intermediates with the appropriate isocyanates and isothiocyanates. The chemical structures of new compounds were confirmed by ^1H-NMR, mass, and elemental analysis. The synthesized compounds were screened for their antibacterial and antifungal activities against some pathogenic strains. Compounds 9a, 9b, 9e, 10a, and 10c, urea derivatives, and compounds 12a and 12d, thiourea derivatives, exhibited a relatively good inhibitory profile against E. coli, with a …

Antimicrobial Properties And Dna Interactions Studies Of 3-Hetarylazoquinoline-2,4-Diol Compounds, Fatma Öztürk, Leyla Açik, İzzet Şener, Fi̇kret Karci, Emi̇ne Kiliç

Turkish Journal of Chemistry

The purpose of the present study was to evaluate the antimicrobial effects of 3-hetarylazoquinoline-2,4-diols (19), having substituted or unsubstituted thiazole, benzothiazole, benzimidazole, triazole, isoxazole, and thiadiazole moieties at the 3-position, on bacterial and yeast strains. In addition, compounds and DNA interaction with pUC18 plasmid DNA were studied. The biological effects of these molecules were compared with potential antibiotics ampicillin,~chloramfenicol (for bacteria), and ketoconozole (for yeast). According to the results, all compounds except 8 have mild to moderate activity against some of the bacterial strains tested, and none of the compounds have activity against the fungi C. tropicalis and C. albicans. …

Novel Biologically Active Glycosides From The Aerial Parts Of Cephalaria Gazipashensis, Nazli Böke Sarikahya, Süheyla Kirmizigül

Turkish Journal of Chemistry

Two new triterpene glycosides, 3-O-\beta-D-glucopyranosyl- (1\to 4)-\beta-D-xylopyranosyl-(1\to 3)-\alpha-L-rhamnopyranosyl- (1\to 3)-\alpha-L-arabinopyranosyl olean-12-ene 28-O-\beta -D- glucopyranosyl-(1\to 6)-\beta-D-glucopyranosyl ester (gazipashoside A, 1) and 3-O-\beta-D-glucopyranosyl-(1\to 4)-\beta-D-xylopyranosyl- (1\to 3)-\alpha-L-rhamnopyranosyl-(1\to 2)-\alpha-L-arabinopyranosyl hederagenin 28-O-\beta -D-glucopyranosyl-(1\to 6)-\beta-D-glucopyranosyl ester (gazipashoside B, 2), were isolated together with 11 known compounds including 7 triterpene, 1 flavonoid, and 3 iridoidal metabolites from the aerial parts of Cephalaria gazipashensis (Dipsacaceae). The structures of all compounds were elucidated by extensive evaluation of the spectroscopic data (1D- and 2D- NMR, HRESI-MS), as well as chemical examinations. The antimicrobial effects of all pure compounds were tested against gram-positive and gram-negative bacteria. The results indicated that the …

Simultaneous Determination Of Cr(Iii) And Cr(Vi) Using Differential Pulse Polarography And Application To Gerede River, Olcay Şendi̇l, Nabeel Mohammed, Güler Somer

Turkish Journal of Chemistry

Determination of Cr(III) in the presence of Cr(VI) from one polarogram is not easy. No such procedure was found in the literature. In polarographic studies Cr(III) had a peak only in acidic medium, while Cr(VI) had either 1 or 2 peaks in both acidic and basic solutions. In solutions that contain these 2 ions, the peak obtained in acidic medium for Cr(III) will be the sum of both ions. Thus, Cr(III) cannot be determined directly from one polarogram. In this work, a new and simple polarographic method is established for the determination of Cr(III) and Cr(VI) by using only one …

Novel Nonresonant And Resonant Mechanisms Leading To The Breakdown Of The Franck-Condon Approximation In Photoionization, David Adam Hardy

LSU Doctoral Dissertations

This thesis attempts to answer the question of how electrons interact with a molecular framework prior to and during emission through photoionization. These studies interrogate several behaviors of allowed and forbidden photoelectron transitions such as shape resonances, non-resonant intrachannel vibronic coupling as a result of Cooper minima, and chemically-induced nonresonant coupling, all of which provide new insights into correlations between the electronic and molecular degrees of freedom. Research presented in this thesis utilizes high-resolution photoelectron spectroscopy, and undulator-based synchrotron radiation at the Advanced Light Source, a synchrotron radiation source in Berkeley, California. Data are collected from near threshold to several …

Plane And Simple: Planar Tetracoordinate Carbon Centers In Small Moleculesw, Chad Crigger, Bernard K. Wittmaack, Marina Tawfik, Gabriel Merino, Kelling J. Donald

Chemistry Faculty Publications

A class of neutral 18-electron molecules with planar tetracoordinate carbon (ptC) centers is introduced. We show computationally that when n = 3 the neutral singlet molecule C(BeH)_n(BH₂)_4-n and other isoelectronic (18-valence electron) molecules of main group elements collapse from locally tetrahedral arrangements at the C-center to (near) planar tetracoordinate structures. For C(BeH)₃BH₂ and C(CH₃)(BH₂)Li₂, for example, the tetrahedral type conformation is not even a minimum on the potential energy surface at the B3PW91, MP2(full), or CCSD levels of theory. The Mg analogue C(MgH)₃BH_{2 …}