Intramolecular Excimer Formation Research Articles

Why linear naphthopyran does not exhibit stable photochromism: A theoretical study

In the present work, we applied our recent hypothesis of intramolecular excimer formation to explain the lack of stable photochromism of linear naphthopyran. To clarify the influence of the stacking interaction between the non-aromatic naphthalene unit and aromatic phenyl ring, a comparative analysis of the results of identical TD-DFT/DFT calculations was performed for angular (3H–) and linear naphthopyrans. In contrary to linear naphthopyran, the open form of 3H-naphthopyran is very stable. The excitations of the closed forms of both naphthopyran isomers are quantitatively and qualitatively close to each other. Optimization of the excited states of the closed forms of both naphthopyran isomers from their FC points leads to the cleavage of C–O bonds and the formation of stacks between the phenyl rings and conjugated rings. The total interaction energy in the intramolecular excimer of 3H-naphthopyran is 17 kcal/mol higher in absolute value than for linear naphthopyran. This difference is due to the significantly greater overlap of rings during stacking in the intramolecular excimer of 3H-naphthopyran compared to linear naphthopyran, since the attraction between the aromatic and non-aromatic systems decreases very strongly with their longitudinal displacement. According to calculations, upon relaxation, 3H-naphthopyran retains the open form with residual stacking while in linear naphthopyran the stacking is destroyed completely, and the molecule returns to the closed form by C–O bond recovery.

Assessing hydrophobic deep eutectic solvents for intramolecular excimer formation.

Intramolecular excimer formation by a dipyrenyl probe, 6-(1-pyrenyl)hexyl-11(1-pyrenyl)-undecanoate [1-Py(CH2)10COO(CH2)61-Py], is used to assess hydrophobic deep eutectic solvents (HDESs) for the purpose. n-Decanoic acid (DA), L(-)-menthol (Men) and thymol (Thy) have been utilized to form HDESs with different pairs of constituents in different molar ratios, namely Men : DA (2 : 1, 1 : 1, and 1 : 2), Thy : DA (2 : 1, 1 : 1, and 1 : 2), and Thy : Men (5 : 1, 2 : 1, 1 : 1, 1 : 2, and 1 : 5). The maximum of the excimer-to-monomer emission intensity ratio, (IE/IM)max, is observed at 343.15-353.15 K for all DESs irrespective of the constitution, and it varies in a narrow range exhibiting no correlation with the dynamic viscosity (η) of the DES which varies between 2.05 and 3.56 mPa s. Excited-state intensity decay data reveal excimer dissociation back to the excited monomer to be negligible in all DESs at lower temperatures (T ≤ 323.15 K); the simplistic Birks scheme is followed at higher temperatures (T > 323.15 K). The rate constant for excimer formation/association, ka, ranges from (3.00 ± 0.50) × 106 s-1 to (103 ± 10) × 106 s-1, which is similar to that reported in other media. The temperature-dependence of the equilibrium constant for excimer formation follows the van't Hoff equation with recovered standard enthalpy (ΔaH*⊖) and standard entropy (ΔaS*⊖) changes, indicating the reversible intramolecular excimer formation to be exothermic and energetically-favorable but entropically unfavorable. A plot of kavs. T/η for all the DES systems investigated exhibits a fairly good linear correlation, indicating the adherence to the Stokes-Einstein formulation within the HDESs further emphasizing the homogeneous nature of the solubilizing media. The work helps to highlight the potential of HDESs for intramolecular excimer formation involving non-polar reactants.

Highly Efficient Intramolecular Excimer Formation in a Disulfide-Linked Dipyrenyl Compound: Proton Recognition and Fluidity Assessment.

Intramolecular excimer formation has been utilized extensively in chemical sciences, especially to probe solvation within complex media as well as to assess physicochemical properties of the solubilizing milieu. Pyrene has been employed extensively as a fluorescence probe for this purpose due to its favorable multidimensional fluorescence properties. Termini-capped dipyrenyl scaffolds possessing various functionalities comprise the majority of such compounds. A new both end-tagged dipyrenyl compound DTP is designed and synthesized, which exhibits significantly high intramolecular excimer formation efficiency in polar solvents. The presence of a -NH-(CO)- and/or -S-S- functionality on the chain linking the two pyrenyl groups facilitates intramolecular excimer formation. Excited-state emission intensity decay reveals that the excimer formation exclusively takes place in the excited state with only one excimer conformation. The rate constant of excimer formation is found to be higher for DTP as compared to a similar compound with an alkyl backbone. The dependence of the excimer formation on the solvent (protic versus aprotic) as well as on temperature reveals further insights into the excimer formation process. The excimer formation by DTP is found to be highly sensitive to the presence of H+: the relative excimer formation efficiency decreases drastically in the presence of a small amount of H+ (∼10-5 M). Further, the recognition of protons by DTP via intramolecular excimer formation is also observed to be highly selective in nature. Based on the observation that both the excimer formation efficiency and kinetics depend on the viscosity of the solubilizing milieu, fluidity assessment of the (dimethyl sulfoxide + acetonitrile) mixture was carried out using DTP. Further, DTP is found to be an effective probe for the assessment of the amount of water in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide as well as in a deep eutectic solvent composed of choline chloride and urea in a 1:2 mol ratio. Highly efficient and rapid intramolecular excimer formation not only establishes DTP as a useful and versatile probe but also offers strategic pathways for designing effective excimer-forming compounds.

Intramolecular dimer formation reveals anomalous solvation within fluorous solvent perfluorodecalin.

Due to the unusual properties of fluorine, a fluorous solvent obtained by replacing hydrogen atoms with fluorine atoms in a hydrocarbon solvent may afford unusual solute solvation and aggregation. A fluorescent dipyrenyl probe, 1,3-bis(1-pyrenyl)propane (BPP), was utilized to explore intramolecular aggregation within perfluorodecalin (PFD), a prototypical fluorous solvent. Steady-state fluorescence emission and excitation along with excited-state emission intensity decay of BPP were acquired in the temperature range of 293.15 to 333.15 K in fluorous solvent PFD and n-hexane-added PFD. The probe BPP is known to form an intramolecular excimer in common hydrocarbon solvents, which is characterized by a broad structureless low-energy emission band; the formation of intramolecular excimers exclusively in the excited state was confirmed via excitation scans along with the intensity decay of the monomer and excimer, respectively. While intramolecular dimerization of BPP does occur in PFD, emission wavelength-dependent excitation spectra and fits of the intensity decay data reveal that intramolecular aggregation takes place in the ground state as well. This ground-state heterogeneity is reduced as the temperature is increased. In the presence of as small as 0.1 mole fraction of n-hexane, the ground-state aggregation vanishes, and intramolecular dimerization again takes place exclusively in the excited state. The data hint at the poor solvation of BPP in PFD to be responsible for intramolecular ground-state aggregation. In PFD-rich (PFD + n-hexane) mixtures, probe pyrene (Py) was found to be preferentially solvated by n-hexane, further corroborating the above-mentioned proposition. Clear differences in solute solvation within a fluorous solvent as compared to hydrocarbon solvents leading to unexpected solubilization and aggregation in fluorous media are amply demonstrated.

Fluorescence of pyrene and its derivatives to reveal constituent and composition dependent solvation within hydrophobic deep eutectic solvents.

Depending on their constituents and composition, deep eutectic solvents (DESs) may exhibit widely varying physicochemical properties. Based on the miscibility of water in a DES, it can broadly be classified as 'hydrophobic' or 'hydrophilic'. The polarity offered by hydrophobic DESs as compared to common organic solvents in the context of solute solubilization thus becomes of the utmost importance. A versatile fluorescence probe, pyrene (Py), its aldehyde derivative, pyrene-1-carboxaldehyde (PyCHO), and a termini end-tagged dipyrenyl polydimethylsiloxane polymer (Py-PDMS-Py) are employed to assess the solvation environment afforded by DESs composed of thymol (Thy), (-)-menthol (Men), and n-decanoic acid (DA). To decipher the effect of the constituents and composition on solute solvation, DESs composed of different pairs of constituents in different molar ratios, namely Thy : Men (1 : 1 and 1 : 2), DA : Men (1 : 1 and 1 : 2), and Thy : DA (2 : 1, 1 : 1, and 1 : 2), are investigated. Pyrene, through its band 1-to-band 3 emission intensity ratio (Py I1/I3), displays higher cybotactic region dipolarity in Thy-containing DESs due to the phenyl ring of Thy; the sensitivity of Py I1/I3 towards temperature is also higher in Thy DESs. The fluorescence lifetime of pyrene and its temperature dependence are higher in Men-containing DESs in comparison. Quenching of pyrene fluorescence by nitromethane in these DESs is dynamic in nature and the recovered bimolecular quenching rate constants (kq) reveal efficient diffusion of the fluorophore-quencher pair in these DESs as compared to other iso-viscous media. The kq adheres to the Stokes-Einstein relation, implying inherent homogeneity associated to these DESs. PyCHO emission spectra show a high energy structured band in Thy : Men DESs, whereas the band shifts bathochromically and becomes broad in DA-containing DESs. The PyCHO cybotactic region is relatively nonpolar in Thy : Men DESs as compared to Thy : DA and Men : DA DESs. The extent of intramolecular excimer formation by Py-PDMS-Py reveals these DESs to be "good" solvents for polymer solvation where DES-polymer interactions are maximized. The microviscosity (ημ) surrounding Py-PDMS-Py correlates with the bulk dynamic viscosity (ηbulk) within the investigated DESs, further corroborating the absence of microheterogeneity. Overall, the observations reveal the similarity of these hydrophobic DESs to common organic solvents in the context of solute solubilization.

Intramolecular H-type dimer and excimer formation in dibenzoylmethanatoboron difluoride dyads connected via diphenylsiloxane linkers

A series of new dibenzoylmethanatoboron difluoride (DBMBF2) and methoxy-substituted DBMBF2 dyads linked via flexible diphenylsiloxane linkers of various length have been synthesized and characterized. The structure and optical properties of these compounds were studied by X-ray single-crystal measurements, electron absorption, and steady-state and time-resolved fluorescence spectroscopy. In the dyads under study, which are in an equilibrium between the open and folded conformations, the formation of intramolecular H-dimers in the ground state are observed. For the dyads in dilute solutions in various solvents, both monomer and excimer (through intramolecular excimer formation) emissions are observed at room temperature. The effect of solvent polarity and linker length on the formation of intramolecular excimers has been studied. The contribution of excimers into the total fluorescence spectrum decreases with increasing the solvent polarity, and the length of the siloxane linker. The studied dyads in hexane and cyclohexane solutions have CIE chromaticity coordinates very close to the white color point. The mechanofluorochromic properties of the synthesized dyads were studied.

Synthesis of Cage-Shaped Borates Bearing Pyrenylmethyl Groups: Efficient Lewis Acid Catalyst for Photoactivated Glycosylations Driven by Intramolecular Excimer Formation.

We describe the synthesis and characterization of a photoactivated boron-based Lewis acid catalyst based on a cage-shaped triphenolic ligand with three pyrenylmethyl moieties. The obtained cage-shaped borate functioned as a photoactivated Lewis acid catalyst thanks to the flexible three pyrenylmethyl moieties. The deformation of the cage-shaped scaffold driven by intramolecular excimer formations of the pyrenes is a critical factor in realizing the photoactivation. Mannich-type reactions and glycosylations significantly were accelerated under 370 nm light irradiations. It is noteworthy that various glycosyl fluorides, which are not easily activated in photocatalytic systems due to their high C-F bond stability, are activated by the photoimproved catalytic activity of the catalyst.

Coherent Intramolecular Excimer Formation in Solid [2,2]‐Paracyclophane: Time‐Resolved Springing of a Molecular “Trap”

AbstractImpulsive UV excitation unleashes violent wave packet motions in [2,2]‐paracyclophane (2PC) due to relief of ground state inter‐ring repulsion. Contrary to theoretical predictions for the benzene excimer, transient absorption spectroscopy in oriented single crystals and in liquid THF demonstrates that excited 2PC absorbs visible light polarized along all three molecular axes. Absorption polarized perpendicular to the aromatic rings is deeply modulated in time by the ∼0.5 Å of light induced inter‐ring breathing providing changes in potential energy gaps and dipole strengths during coherent intramolecular excimer formation. Overlapping transitions to several higher electronic states and strong non‐Condon effects contribute to the modulating spectra. These insights prove current understanding of the simplest archetypal organic excimer is fundamentally flawed and provide the basis for testing improved electronic structure models. It is hard to overestimate the significance of achieving such improved understanding given the impact of excimers and exciplexes on all aspects of organic molecular photophysics.

Excimer Formation of Perylene Bisimide Dyes within Stacking-Restrained Folda-Dimers: Insight into Anomalous Temperature Responsive Dual Fluorescence

Excimer Formation of Perylene Bisimide Dyes within Stacking-Restrained Folda-Dimers: Insight into Anomalous Temperature Responsive Dual Fluorescence

Folded Perylene Diimide Loops as Mechanoresponsive Motifs.

A supramolecular mechanophore that can be integrated into polymers and indicates deformation by a fluorescence color change is reported. Two perylene diimides (PDIs) were connected by a short spacer and equipped with peripheral atom transfer polymerization initiators. In the idle state, the motif folds into a loop and its emission is excimer dominated. Poly(methyl acrylate) (PMA) chains were grown from the motif and the mechanophore-containing polymer was blended with unmodified PMA to afford materials that display a visually discernible fluorescence color change upon deformation, which causes the loops to unfold. The response is instant, and correlates linearly with the applied strain. Experiments with a reference polymer containing only one PDI moiety show that looped mechanophores that display intramolecular excimer formation offer considerable advantages over intermolecular dye aggregates, including a concentration-independent response, direct signaling of mechanical processes, and a more pronounced optical change.

Folded Perylene Diimide Loops as Mechanoresponsive Motifs

AbstractA supramolecular mechanophore that can be integrated into polymers and indicates deformation by a fluorescence color change is reported. Two perylene diimides (PDIs) were connected by a short spacer and equipped with peripheral atom transfer polymerization initiators. In the idle state, the motif folds into a loop and its emission is excimer dominated. Poly(methyl acrylate) (PMA) chains were grown from the motif and the mechanophore‐containing polymer was blended with unmodified PMA to afford materials that display a visually discernible fluorescence color change upon deformation, which causes the loops to unfold. The response is instant, and correlates linearly with the applied strain. Experiments with a reference polymer containing only one PDI moiety show that looped mechanophores that display intramolecular excimer formation offer considerable advantages over intermolecular dye aggregates, including a concentration‐independent response, direct signaling of mechanical processes, and a more pronounced optical change.

Synthesis and properties of new dibenzoylmethanatoboron difluoride dyads connected by flexible siloxane linkers

A series of novel dibenzoylmethanatoboron difluoride (DBMBF2) and methoxy-substituted DBMBF2 dyads linked via flexible dimethylsiloxane linkers of variable length were synthesized and characterized. Both monomer and excimer (trough intramolecular excimer formation) emissions are observed for the dyads in dilute dichloromethane solutions at room temperature. The excimers contribution into the total fluorescence spectrum decreases with increasing siloxane linker length. The parallel-sandwich conformation of intramolecular pre-excimers formed by two terminal DBMBF2 moieties is confirmed by DFT-based calculations.

Switching of Fluorescent Zn/Cd Selectivity in N,N,N',N'-Tetrakis(6-methoxy-2-quinolylmethyl)-1,2-diphenylethylenediamine by One Asymmetric Carbon Atom Inversion.

A quinoline-based hexadentate ligand, (S,S)-N,N,N',N'-tetrakis(6-methoxy-2-quinolylmethyl)-1,2-diphenylethylenediamine ((S,S)-6-MeOTQPh2EN), exhibits fluorescence enhancement at 498 nm upon addition of 1 equiv of Zn2+ (IZn/I0 = 12, φZn = 0.047) in aqueous DMF solution (DMF/H2O = 2:1). Addition of 1 equiv of Cd2+ affords a much smaller fluorescence increase at the same wavelength (ICd/I0 = 2.5, ICd/IZn = 21%). The trivalent metal ions such as Al3+, Cr3+, and Fe3+ also exhibit fluorescence enhancement at 395 nm (IAl/I0 = 22, ICr/I0 = 6 and IFe3+/I0 = 13). In contrast, meso-6-MeOTQPh2EN exhibits a Cd2+-selective fluorescence increase at 405 nm in the presence of 1 equiv of metal ion (ICd/I0 = 11.5, φCd = 0.022), while Zn2+ induces a smaller fluorescent response under the same experimental conditions (IZn/I0 = 3.3, IZn/ICd = 29%). In this case, the fluorescence intensities of meso-6-MeOTQPh2EN in the presence of a large amount of Zn2+ and Cd2+ become similar. This diastereomer-dependent, fluorescent metal ion specificity is derived from the Zn2+-specific intramolecular excimer formation in (S,S)-6-MeOTQPh2EN-Zn2+ complex and higher binding affinity of meso-6-MeOTQPh2EN with Cd2+ in comparison to Zn2+. The more conformationally restricted diastereomeric pair, namely, cis- and trans-TQDACHs (cis- and trans-N,N,N',N'-tetrakis(2-quinolylmethyl)-1,2-diaminocyclohexanes), both exhibit Zn2+-specific fluorescence enhancement because of the high metal binding affinity and intramolecular excimer forming property derived from the rigid DACH backbone.

An AIEE active 1, 8-naphthalimide- sulfamethizole probe for ratiometric fluorescent detection of Hg2+ ions in aqueous media

1,8-Naphthalimide-based sulfamethizole molecule (L6) has been designed and synthesized which have properties like AIEE active, and ratiometric fluorescence sensing of Hg2+ and Ag+ ions. The hydrophobic nature of naphthalimide fluorogenic moiety instigates the aggregation induced emission (AIE) in aqueous medium, led to excimer emission upon intramolecular excimer formation via metal ion-induced assembly. The high selectivity of the sensor was due to quenching of the monomeric emission of L6 at 390 nm with red shift to gradual enhancement in new peak at 483 nm and 478 nm for Hg2+ and Ag+ ions respectively, which is responsible for the ratiometric detection. The competitive experiments revealed that the chemosensor is selective to Hg2+ over Ag+ ion and selective and sensitive ratiometric response to Hg2+ ion without interference of any other metal ions. A limit of detection of Hg2+ ion was found 14.7 nM in 99 % aqueous solution. Also, the visual fluorescence color change of L6 from blue to green was observed under uv-lamp upon addition of Hg2+ ion to L6 solution.

Near‐Infrared Circularly Polarized Luminescence through Intramolecular Excimer Formation of Oligo(p‐phenyleneethynylene)‐Based Double Helicates

AbstractInvited for the cover of this issue is the group of Koji Miki, Kouichi Ohe, and colleagues at Kyoto University. The image depicts mythical dragons as carbon‐based double helicates. Read the full text of the article at 10.1002/chem.201901467.

Near-Infrared Circularly Polarized Luminescence through Intramolecular Excimer Formation of Oligo(p-phenyleneethynylene)-Based Double Helicates.

Carbon-based double helicates consisting of two anthracene-containing oligo(p-phenyleneethynylene) units and two flexible chiral 1,1'-binaphthyl units or two rigid chiral 9,9'-spirobifluorene units were developed. The curved oligo(p-phenyleneethynylene) fragments in the double helicates were successfully constructed by tin-mediated reductive aromatization. Helical oligo(p-phenyleneethynylene) double strands fixed by two rigid spirobifluorene units showed little structural change under photoirradiation, thereby emitting circularly polarized luminescence (CPL) in the visible region with a high quantum yield (ΦPL =0.93). In contrast, flexible binaphthyl units induced dynamic structural change of the oligo(p-phenyleneethynylene) luminophores under photoirradiation, leading to strong CPL (|glum |=1.1×10-2 ) in the near-infrared (NIR) region. UV/Vis, circular dichroism (CD), CPL and NMR spectroscopic analyses of the binaphthyl-hinged double helicate suggested excimer formation between two π-conjugated strands in the excited state. Theoretical calculations highlight the importance of the tightly interlocked excimer structure of the carbon-based double helicate in controlling the angle between the electric and magnetic transition dipole moments for strong NIR CPL generation.

Mechanochromism induced through the interplay between excimer reaction and excited state intramolecular proton transfer

Excited-state intramolecular proton transfer (ESIPT) and excimer formation are unimolecular and bimolecular reactions, respectively. The coupling between these two reactions has been rarely observed. Here we show the interplay between ESIPT and excimer formation in CF3-HTTH (2,2′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(4-(trifluoromethyl)phenol) solid crystal, resulting in the extensively broad multiple emissions spanning from 420 to 750 nm. Comprehensive structural, time-resolved spectroscopic, and two-photon microscopic studies of CF3-HTTH in crystal lattice unveil the pre-equilibrium ESIPT between the normal (N*) and tautomer (T*) form, for which the slow population decay and well-ordered lattice packing facilitate excimeric (E*) formation, rendering N* (460 nm), T* (520 nm) and E* (600 nm) triple emissions. In contrast, the lower degree of packing on the solid surface prohibits excimer formation, showing only the ESIPT process. The correlation between luminescence properties and packing structure sheds light on the corresponding mechanochromic effect based on molecular solid architecture and provide new insight into the aggregation-induced properties.

New cyclotriphosphazene based nanotweezers bearing perylene and glycol units and their non-covalent interactions with single walled carbon nanotubes

We report on the design, synthesis and characterization of three new amphiphilic four fragment cyclotriphosphazene nanotweezers based on thermally stable carrier/router cyclotriphosphazene, extended polycyclic aromatic perylene bisimides with hydrophobic aliphatic tail and solvophilic glycol units, suitable for the exfoliation of single-walled carbon nanotubes (SWCNTs). The ultrasonication of SWCNT and new cyclotriphosphazene derivatives provided disentangled and undamaged SWCNTs, which interact with the perylene units through π–π interactions. The newly synthesized perylene-cyclotriphosphazenes were characterized by elemental analysis, mass, 31P, 1H and 13C NMR techniques. The photophyisical behavior of cyclotriphosphazene derivatives and their nanocomposites were investigated via UV– Vis absorption and fluorescence emission spectroscopy. It was found that non-geminal- cis-tris- perylenebisimide substituted compound exhibit an additional fluorescence peak compared with the parent compounds which is consistent with an intramolecular excimer formation. Prepared nanocomposites were also characterized via Raman spectroscopy and the morphological features were analyzed by HR- TEM. The quality of the nanocomposite dispersions in water were evaluated by zeta potential analysis.

Pyrophosphate-Induced Intramolecular Excimer Formation in Dinuclear Zinc(II) Complexes with Tetrakisquinoline Ligands

Dinuclear Zn2+ complexes with HTQHPN ( N,N,N' ,N'-tetrakis(2-quinolylmethyl)-2-hydroxy-1,3-propanediamine) derivatives have been prepared, and their pyrophosphate (PPi, P2O74-) sensing properties were examined. The ligand library includes six HTQHPN derivatives with electron-donating/withdrawing substituents, an extended aromatic ring, and six-membered chelates upon zinc binding. Complexation of ligand with 2 equiv of Zn2+ promotes small to moderate fluorescence enhancement around 380 nm, but in the cases of HTQHPN, HT(6-FQ)HPN ( N,N,N' ,N'-tetrakis(6-fluoro-2-quinolylmethyl)-2-hydroxy-1,3-propanediamine), and HT(8Q)HPN ( N,N,N' ,N'-tetrakis(8-quinolylmethyl)-2-hydroxy-1,3-propanediamine), subsequent addition of PPi induced a significant fluorescence increase around 450 nm. This fluorescence enhancement in the long-wavelength region is attributed to the conformational change of the bis-(quinolylmethyl)amine moiety which promotes intramolecular excimer formation between adjacent quinolines upon binding with PPi. The structures of PPi- and phosphate-bound dizinc complexes were revealed by X-ray crystallography utilizing phenyl-substituted analogues. The zinc complex with HT(8Q)HPN exhibits the highest signal enhancement ( IPPi/ I0 = 12.5) and selectivity toward PPi sensing ( IATP/ IPPi = 20% and IADP/ IPPi = 25%). The fluorescence enhancement turned to decrease gradually after the addition of more than 1 equiv of PPi due to the removal of zinc ion from the ligand-zinc-PPi ternary complex, allowing the accurate determination of PPi concentrations at the fluorescence maximum composition. The practical application of the present method was demonstrated monitoring the enzymatic activity of pyrophosphatase.

Pyrene functionalized cyclotriphosphazene-based dyes: Synthesis, intramolecular excimer formation, and fluorescence receptor for the detection of nitro-aromatic compounds

A series of pyrene functionalized cyclotriphosphazene-based dyes, mono- (1), cis- and trans-non-geminal-bis (2a, 2b), geminal-bis-(4), geminal-tetrakis-(6), and hexakis-(7) derivatives, has been synthesized and, their photophysical properties such as molar absorption coefficients (ε), fluorescence emission, fluorescence quantum yields (ϕF) and fluorescence lifetimes (τF) have been investigated. On the relationship between molecular geometry and emission properties of dyes has been also discussed. It was found that bis-pyrene substituted compounds (2a, 2b and 4) exhibited three different fluorescence spectra which consisted of an excimer, a monomer and both monomer and excimer emissions in the same solvents, respectively. The emission difference between 2a and 2b clearly revealed that intramolecular excimer formation, which permitted to characterize unambiguously as a cis-isomer, observed for compound 2a whereas 2b showed only monomer emission and consequently as a trans-isomer. These formation behaviors were supported by DFT calculation with wB97XD/6-31G (d, p) and 31P NMR spectroscopy on addition of chiral solvating agent (CSA) experimental studies. Additionality, sensing behaviors of 2a, 4 and 6 were investigated for the detection of nitro aromatic compounds (NACs). It was found that the fluorescence emissions of the compounds were significantly quenched in presence of TNT, nitrobenzene or nitrophenol, while other tested metal ions induced no spectral changes.