Dimethylamino Naphthalene Research Articles

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene.

A set of novel 1,4-diaryl-1,3-butadiynes terminated by two 7-(arylethynyl)-1,8-bis(dimethylamino)naphthalene fragments was prepared via the Glaser-Hay oxidative dimerization of 2-ethynyl-7-(arylethynyl)-1,8-bis(dimethylamino)naphthalenes. The oligomers synthesized in this way are cross-conjugated systems, in which two conjugation pathways are possible: π-conjugation of 1,8-bis(dimethylamino)naphthalene (DMAN) fragments through a butadiyne linker and a donor-acceptor aryl-C≡C-DMAN conjugation path. The conjugation path can be "switched" simply by protonation of DMAN fragments. X-ray diffraction, UV-vis spectroscopy and cyclic voltammetry are applied to analyze the extent of π-conjugation and the efficiency of particular donor-acceptor conjugation path in these new compounds. X-ray structures and absorption spectra of doubly protonated tetrafluoroborate salts of the oligomers are also discussed.

Understanding water dynamics in different subcellular environments by combining multiplexing imaging and dimethylamino naphthalene fluorescent derivatives

Water dynamics in different subcellular locations are crucial to modulate several cellular processes such as enzyme function, membrane dynamics, and phase separation. Methods to study water dynamics at subcellular level in vivo are scarce and technically challenging. The environmentally sensitive fluorescent probes derived from dimethylaminonaphthalene (DAN) were designed to sense polarity and dipolar relaxation around its proximity and address macromolecules' structural dynamics. In this work, we used four different DAN probes: LAURDAN, PRODAN, ADCAN, and DANCA, with a differential affinity for different subcellular locations due to its functional group included in the carbonyl group.

A new family of 1,4-diaryl-1,3-butadiynes based on the “proton sponge”: synthesis, electronic and chemical properties

A new family of 1,4-diaryl-1,3-butadiynes containing two and four fragments of 1,8-bis(dimethylamino)naphthalene (“proton sponge”) were synthesized.

Novel and Polynuclear K- and Na-Based Superalkali Hydroxides as Superbases Better Than Li-Related Species and Their Enhanced Properties: An Ab Initio Exploration.

Hydroxides of superalkalis (particularly, K- and Na-related species) are shown for the first time to function as superbases. A new small series of hydroxides (XMn+1OH) is designed based on superalkali species (XMn+1) where M (K and Na) is alkali metal atoms, n is the maximal formal valence of the central atom X (F, O, and N), and n ≥ 1. To probe whether such fascinating polynuclear superalkali hydroxides (SAHs), especially the K- and Na-associated moieties are as basic as the representative alkali metal hydroxides (KOH, NaOH, and LiOH) as well as similar Li-based SAHs, a comprehensive computational exploration (in the gas phase) has been reported using the framework of an ab initio method. The ab initio calculations reveal that both the K- and Na-related SAHs consisting of larger gas-phase proton affinity (PA) and gas-phase basicity (GB) values demonstrate stronger basic character compared to the LiOH and Li-based SAHs. However, the available SAHs act as strong bases as well as superbases; among the proposed K- and Na-based SAHs, remarkably, the OK3OH moiety having the highest PA (1168.4 kJ/mol) and GB (1146.9 kJ/mol) values shows the evidence of the strongest basicity (i.e., superbase/hyperbase), which exceed enough (ΔPA: 142.1 kJ/mol and ΔGB: 146.9 kJ/mol) the IUPAC-defined superbasicity threshold values (PA: 1026.3 kJ/mol and GB: 1000 kJ/mol) of 1,8-bis(dimethylamino)naphthalene (DMAN). Furthermore, theoretical signatures have been predicted via the electronic structure calculation approach in probing the dissociation energy, ionization potential, electron affinity, HOMO–LUMO gap, and chemical hardness as well as the NCI plot and QTAIM tools are used for the bonding feature analysis and such parameters are well linked with the basicity analyzing parameters. In this study, the ab initio-based computational experiments provide some new insights into the basicity features and understanding of the structural and electronic features of a small series of designed K- and Na-related SAHs. Design and synthesis of such theoretically examined SAHs may pave alternative routes for the experimentally rewarding applications.

Lithiation of 2,4,5,7-Tetrabromo-1,8-bis(dimethylamino)naphthalene: Peculiarities of Directing Groups’ Effects and the Possibility of Polymetalation

Lithiation of 2,4,5,7-Tetrabromo-1,8-bis(dimethylamino)naphthalene: Peculiarities of Directing Groups’ Effects and the Possibility of Polymetalation

Symmetry/Asymmetry of the NHN Hydrogen Bond in Protonated 1,8-Bis(dimethylamino)naphthalene

Experimental and theoretical results are presented based on vibrational spectra and motional dynamics of 1,8-bis(dimethylamino)naphthalene (DMAN) and its protonated forms (DMANH+ and the DMANH+ HSO4− complex). The studies of these compounds have been performed in the gas phase and solid-state. Spectroscopic investigations were carried out by infrared spectroscopy (IR), Raman, and incoherent inelastic neutron scattering (IINS) experimental methods. Density functional theory (DFT) and Car–Parrinello molecular dynamics (CPMD) methods were applied to support our experimental findings. The fundamental investigations of hydrogen bridge vibrations were accomplished on the basis of isotopic substitutions (NH → ND). Special attention was paid to the bridged proton dynamics in the DMANH+ complex, which was found to be affected by interactions with the HSO4− anion.

Phase-selective staining of model and cell membranes, lipid droplets and lipoproteins with fluorescent solvatochromic pyrene probes

The push-pull solvatochromic pyrene derivatives PA and PK have been applied to the study of model membrane vesicles, cells and purified human serum lipoproteins, using both confocal fluorescence microscopy and fluorescence spectroscopy. These polarity-sensitive probes provide information similar to that obtained by Laurdan or Prodan, i.e. mainly lipid order in biomembranes, but they have the essential advantage of being excitable by a standard 405 nm laser light, bypassing the use of multiphoton excitation. In addition, they are brighter and much more photostable than those dimethylamino naphthalene derivatives. Our results with model membrane spectroscopy (multilamellar vesicles) and with microscopy (giant unilamellar vesicles) showed the capacity of PA and PK to report differently on liquid-disordered, liquid-ordered and gel phase bilayers. Moreover, a ratiometric parameter, the Red/Blue Intensity Ratio (RBIR) could be used for inter-domain, inter-vesicle and even inter-technique comparison, and the appropriate microscopy-spectroscopy conversion coefficients could be estimated. In studies at the cellular level, PA probe stained almost exclusively the plasma membrane of red blood cells, revealing its high degree of lipid order. Using Chinese Hamster Ovary cells PA was shown to be an excellent probe for the detection of cytoplasmic lipid droplets, superior to Nile Red in that PA provides simultaneously a detailed information of membrane order in the whole cell, in which the lipid droplets appear with a very good contrast. Moreover, spectrofluorometric data of PA-stained serum lipoproteins indicated an essentially identical value of RBIR for lipid droplets and for high-density lipoproteins.

N-Methylated 1,8-Diaminonaphthalenes as Bifunctional Nucleo­philes in Reactions with α,ω-Dihalogenoalkanes: A Facile Route to Heterocyclic and Double Proton Sponges

The reaction of 1-dimethylamino-8-(methylamino)naphthalene with 1,3-dibromopropane chemoselectively leads to the product of N,N′-heterocyclization, while in the case of 1,4-dibromobutane and 1,2-bis(bromomethyl)benzene the process results in heterocyclization onto the same nitrogen atom with the formation of previously unknown 1-dimethylamino-8-pyrrolidino- and 1-dimethylamino-8-isoindolino-naphthalenes. The same reactions conducted without adding any auxiliary base lead to the formation of N,N′-linked double proton sponges as a new type of polynitrogen organic receptor. Proceeding as a sequence of quaternization–demethylation–cyclization steps, this heterocyclization process can also be used to construct six-membered rings (piperidino, morpholino), albeit in lower yields. The ability of 1,2-dibromoethane to brominate N-alkylated 1,8-diaminonaphthalenes is also described. It is shown for the first time that a commercially available 1,8-bis(dimethylamino)naphthalene (DMAN) can be used as a starting material in a heterocyclization reaction, which via a one-pot approach and in a short time can be converted into 1,5-dimethylnaphtho[1,8-bc]-1,5-diazacyclooctane or 1-dimethylamino-8-(pyrrolidin-1-yl)naphthalene.

Theoretical study of intramolecular hydrogen bond in selected symmetric "proton sponges" on the basis of DFT and CPMD methods.

"Proton sponges," derivatives of prototypic 1,8-bis(dimethylamino)naphthalene (DMAN), exhibit remarkable basicity, which made them interesting for various experimental and theoretical studies. The details of bridged proton dynamics in protonated DMAN and its derivative denoted as TMGN (1,8-bis(tetramethylguanidino)naphthalene) were investigated on the basis of density functional theory (DFT) and Car-Parrinello molecular dynamics (CPMD) methods. Special attention was paid to the effects of symmetry of the molecular skeleton and the type of substituent on the bridged proton neighborhood statistics and dynamics. The metric parameter analyses of hydrogen bridge provided us with a conclusion that proton migration events in TMGNH+ are less numerous than in DMANH+, which can be rationalized by noticing the slower dynamics of large substituents of TMGN with respect to the smaller -N(Me)2 groups of DMAN. The atomic velocity power spectra served as computational models of the vibrational signatures associated with the presence of the intramolecular hydrogen bond. A broad feature was registered for hydrogen bonds present in both compounds. The computations were verified by experimental data available.

Dimethylamino naphthalene-based cyanostyrene derivatives with stimuli responsive luminescent properties

Stimuli-responsive organic luminescent materials have attracted increasing attention for their specific chemical and physical properties and potential application in many fields, such as sensing materials, optoelectronic devices and security papers. In this work, we designed and synthesized three new organic smart materials with dimethylamino naphthalene and cyanostyrene moieties. These fluorescent molecules show solvatochromic properties. With solvent polarity increased, their fluorescent emissions are red shifted. These molecules also exhibited aggregation-induced emission enhancement properties. The emission wavelength of these materials in solid state was red-shifted upon stimuli with external mechanic force, which could be recovered after addition of dichloromethane solvent. The PXRD and DSC experiments revealed that the mechanochromic properties could be ascribed to the phase transition between crystalline and amorphous states. The switch of optical properties of these molecules under acid stimuli was also studied. The fluorescent emissions show blue-shifted when exposed to trifluoroacetic acid, and these organic materials were further utilized as security ink.

(2-Benzyloxyphenyl)acetyl (BnPAc): A Participating Relay Protecting Group for Diastereoselective Glycosylation and the Synthesis of 1,2-trans Glycosyl Esters

The (2-benzyloxyphenyl)acetyl group has been identified as a new protecting group for hydroxyl functions. Various alcohols could be easily protected with high yields, and deprotection was achieved by a relay approach using Pd/H2 in combination with 1,8-bis(dimethylamino)naphthalene, conditions that are orthogonal to ester groups. The new protecting group is stable in glycosylation reactions demonstrating an effective neighboring group participation leading to the exclusive formation of 1,2-trans glycosides and glycosyl esters.

Strategic Design and Utilization of Molecular Flexibility for Straddling the Application of Organic Superbases: A DFT Study

AbstractThe density functional theory (DFT) calculations were performed for a series of new molecular frameworks that have potential to work as organic superbases. In the present report, we have exploited and strategically substituted 2 and 6 positions of the pyridine by a potential anchoring group, 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD). The value of proton affinities (PAs) of the molecular frameworks was calculated in the gas phase as well as in acetonitrile solution. The designed non‐ionic and neutral organic superbases were found to have higher basicity than that of the benchmarked molecule, 1,8‐bis(dimethylamino)‐naphthalene (DMAN). The zero‐point vibrational energy (ZPVE) and PAs values were calculated for the designed molecular frameworks at B3LYP/6‐311+G**//B3LYP/6‐31+G* level of theory. For compression, we have also performed the optimization of all the structures at M06‐2X/6‐311 +G**//M06‐2X/6‐31+G* level of theory. The molecular framework 9 has highest PAs values 1151.2 and 1246.3 kJ mol−1 in the gas phase and in acetonitrile solution, respectively at B3LYP/6‐311+G**//B3LYP/6‐31+G* level of theory. The designed molecular frameworks have better flexibility, which enables it for selective extraction of the smaller to larger size molecules by varying the size of the cavity, as required for the various applications. In this context, we have explored the application of designed molecular frameworks for the selective extraction of UO22+ over VO2+.

Laying the way to meta-functionalization of naphthalene proton sponge via the use of Schlosser's superbase

Lithiation of 1,8-bis(dimethylamino)naphthalene (DMAN) with Schlosser's superbase (n-BuLi–t-BuOK) in the presence of TMEDA in hexane was examined. It has been shown that, compared with previously studied n-BuLi–TMEDA or t-BuLi–TMEDA mixtures, this reagent provides much more selective meta-lithiation. A variety of 3-substituted and 3,6-disubstituted derivatives of DMAN has been prepared in a good to reasonable yield after quenching the reaction mass with different electrophiles. A possibility of further functionalization of thus introduced meta-substituents to synthesize more complex 3-substituted derivatives of DMAN is also demonstrated.

Synthesis and electroluminescent property of highly efficient phosphorescent red dopants based on modulated main ligands

ABSTRACTNovel red phosphorescent iridium(III) complexes, (DPAP-MQ)2Ir(tmd), (DMAP-MQ)2Ir(tmd), (PN-MQ)2Ir(tmd) were synthesized for red emitter of the phosphorescent organic light-emitting diodes (phOLEDs). The ligands have sites of both the electron donor and acceptor in a molecule. The main ligands consisted of electron-donors ((dimethylamino)phenyl, (diphenylamino)phenyl, (dimethylamino)naphthalene) and electron-acceptor methyl quinoline were synthesized by suzuki coupling reaction. The iridium(III) complexes based on main ligands and 2,2,6,6-tetramethyl-3,5-heptanedione(tmd) ancillary ligand were synthesized by Nonoyama reaction. Their luminescence property was investigated by UV-visible spectroscopy and photoluminescence (PL) spectroscopy. The manufactured PHOLEDs were characterized by investigation of current density-voltage-luminance, luminance efficiency, external quantum efficiency, electroluminescence spectrum. These phosphorescent iridium complexes will be promising candidates for highly efficient red emitters.

Metal Insertion in a Methylamine-Functionalized Zirconium Metal-Organic Framework for Enhanced Carbon Dioxide Capture.

The reaction of ZrCl4 with 2',3',5',6'-tetramethylamino-p-terphenyl-4,4″-dicarboxylic acid (H2tpdc-4CH2NH2·3HCl) in the presence of NaF affords Zr6O4(OH)2.1F1.9(tpdc-4CH2NH2·3HCl)6 (1), which is a new member of the Zr6O4(OH)4(dicarboxylate linker)12 or UiO-68 family, and exhibits high porosity with BET and Langmuir surface areas of 1910 m2/g and 2220 m2/g, respectively. Remarkably, fluoride ion incorporation in the zirconium clusters results in increased thermal stability, marking the first example of enhancement in the stability of a UiO framework by this defect-restoration approach. Although material 1 features four alkylamine groups on each organic linker, the framework does not exhibit the high CO2 uptake that would be expected for reaction between CO2 and the amine groups to form carbamic acid or ammonium carbamate species. The absence of strong CO2 adsorption can likely be attributed to protonation at some of the amine sites and the presence of counterions. Indeed, exposure of material 1 to acetonitrile solutions of the organic bases 1,8-bis(dimethylamino)naphthalene (DMAN) or trimethylamine, affords a partially deprotonated material, which exhibits enhanced CO2 uptake. Exposure of basic amine sites also facilitates the postsynthetic chelation of copper(I) ([Cu(MeCN)4]·CF3SO3) to yield material 2 with an enhanced CO2 uptake of 4 wt % at 0.15 bar, which is double that of the parent framework 1.

Using aromatic polyamines with high proton affinity as "proton sponge" dopants for electrospray ionisation mass spectrometry.

Proton sponges are polyamines with high proton affinity that enable gentle deprotonation of even mildly acidic compounds. In this study, the concept of proton sponges as signal enhancing dopants for electrospray ionisation is presented for the first time. 1,8-Bis(dimethylamino)naphthalene (DMAN) and 1,8-bis(tetramethylguanidino)naphthalene (TMGN) were chosen as dopants, using methanol and acetonitrile/methanol as solvents. Individual standard compounds, compound mixtures and a diesel fuel as a complex sample matrix were investigated. Both proton sponges enhanced signal intensities in electrospray ionisation negative mode, but TMGN decomposed rapidly in methanolic solution. Significantly higher signals were only achieved using the acetonitrile/methanol mixture. On average a more than 10-fold higher signal intensity was measured with 10-3 mol l-1 DMAN concentration. A stronger signal increase of alcohol functionalities was observed compared to acid functionalities. All compound classes which were detected in the diesel fuel (CH- and CHOx-class) received roughly 100-fold higher signal intensities when using DMAN as a dopant. Furthermore, the number of detected compounds as well as the double bond equivalent of the detected compounds increased. The compound class distribution shifted when adding DMAN and the formerly dominant CHO2-, CHO3-, and CHO4- classes received similar relative intensities as formerly less accessible classes. The findings depict DMAN as a promising additive for electrospray ionisation negative analysis of at least mildly acidic compounds, even within complex sample material.

Analysis of naphthenic acids by matrix assisted laser desorption ionization time of flight mass spectrometry

We report on a matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF) method to analyze naphthenic acids (NAs), from petrochemical samples, using 9-aminoacridine (9-AA) and a proton sponge 1,8-bis(dimethylamino) naphthalene (DMAN), as matrices. Singly charged deprotonated molecules of NAs, [M−H]−, dominated the negative ion MALDI mass spectra. The negative ions were pre-formed in solution through an acid/base Brönsted-Lowry reaction promoted by the highly basic matrices (9-AA and DMAN). The DMAN afforded cleaner spectra with absence of clusters, aggregates or matrix interferences at low m/z; in addition, it provides molecular weight distributions similar to those observed with negative ion electrospray ionization (ESI). In contrast, MALDI spectra obtained with 9-AA exhibits matrix interferences at low mass, and bias towards aliphatic NAs. Finally, we observe the presence of monomeric species in the low mass region and non-covalent aggregates at higher masses in the negative mode MALDI spectra with both matrices, much like with negative mode ESI. We demonstrate that MALDI-TOF/MS is a viable tool for NAs analyses with added advantages such as high throughput and exceptional tolerance to the presence of impurities and salts in the samples, when compared with ESI.

Engineering Short, Strong, Charge-Assisted Hydrogen Bonds in Benzoic Acid Dimers through Cocrystallization with Proton Sponge

A series of molecular complexes of the proton sponge 1,8-bis(dimethylamino)naphthalene (DMAN) with monosubstituted halobenzoic acids are reported, illustrating the designed exploitation of the characteristics of the proton sponge to induce short, charge-assisted hydrogen bonds in a predictable and reproducible manner. In every case, a DMAN molecule extracts a proton from the carboxylic acid group of the benzoic acid, as a result of which a recurrent supramolecular unit between a neutral and a deprotonated benzoic acid molecule is formed, featuring an extremely short, strong O–H···O hydrogen bond, within a predominant crystallization ratio of 1:2 (DMAN:benzoic acid).

(15)N and (1)H Solid-State NMR Investigation of a Canonical Low-Barrier Hydrogen-Bond Compound: 1,8-Bis(dimethylamino)naphthalene.

Strong or low-barrier hydrogen bonds have often been proposed in proteins to explain enzyme catalysis and proton-transfer reactions. So far (1)H chemical shifts and scalar couplings have been used as the main NMR spectroscopic signatures for strong H-bonds. In this work, we report simultaneous measurements of (15)N and (1)H chemical shifts and N-H bond lengths by solid-state NMR in (15)N-labeled 1,8-bis(dimethylamino)naphthalene (DMAN), which contains a well-known strong NHN H-bond. We complexed DMAN with three different counteranions to examine the effects of the chemical environment on the H-bond lengths and chemical shifts. All three DMAN compounds exhibit significantly elongated N-H distances compared to the covalent bond length, and the (1)H(N) chemical shifts are larger than ∼17 ppm, consistent with strong NHN H-bonds in the DMAN cation. However, the (15)N and (1)H chemical shifts and the precise N-H distances differ among the three compounds, and the (15)N chemical shifts show opposite dependences on the proton localization from the general trend in organic compounds, indicating the significant effects of the counteranions on the electronic structure of the H-bond. These data provide useful NMR benchmarks for strong H-bonds and caution against the sole reliance on chemical shifts for identifying strong H-bonds in proteins since neighboring side chains can exert influences on chemical shifts similar to those of the bulky organic anions in DMAN. Instead, N-H bond lengths should be measured, in conjunction with chemical shifts, as a more fundamental parameter of H-bond strength.

Crystal structures of 1,8‐bis(dimethylamino)naphthalene (DMAN) and dicarboxylic acids complexes determined from single‐crystal and powder diffraction data

New complexes of DMAN proton sponge with 3 dicarboxylic acids (dca): glutaric {1}, suberic {2} and dodecanedioic acid {3} were obtained. The structures of the complexes {1,2} were solved on the basis of laboratory powder data, while the structure of {3} was solved using single crystal methods. The additional goal of the study was to test some new approaches to organic crystal structure solution from powder diffraction data, particularly with presence of molecules with high number of internal rotational degrees of freedom (dca molecules). Performance of structure solution using the popular FOX program was tested with alternative definitions of flexible dca molecules.