Conformationally Rigid EthynyleneâCumulene Conjugated Aromatic

Subscriber access provided by UNIV OF NEW ENGLAND ARMIDALE

Article

Conformationally rigid Ethynylene-Cumulene Conjugated Aromatic [30] Heteroannulenes with NIR Absorption: Synthesis, Spectroscopic and Theoretical Characterization Krushna Chandra Sahoo, Meenakshi S Kumaraswami, Dandamudi Usharani, and Harapriya Rath J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b00180 • Publication Date (Web): 01 Apr 2019 Downloaded from http://pubs.acs.org on April 1, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Organic Chemistry

Conformationally

rigid

Ethynylene-Cumulene

Conjugated Aromatic [30] Heteroannulenes with NIR Absorption: Synthesis, Spectroscopic and Theoretical Characterization Krushna Chandra Sahoo,Ϯ Meenakshi S Kumaraswami,§ Dandamudi Usharani,

§†*

and

Harapriya Rath Ϯ* Ϯ

School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A/2B

Raja S. C. Mullick Road, Jadavpur, Kolkata 700032(India) §

Department of food safety and Analytical Quality Control Laboratory, CSIR-Central Food

Technological Research Institute, Mysuru 700020 Karnataka, India †Academy

of Scientific and Innovative Research (AcSIR), CSIR-HRDC, Ghaziabad, Uttar Pradesh, India

[email protected] [email protected]

ABSTRACT

Two hitherto unknown conformationally rigid Hückel aromatic ethynylene-cumulene conjugated [30] heteroannulenes have been synthesized and characterized. A thorough solution-state spectroscopic characterization, combined with in-depth theoretical calculations has been performed to arrive at the proposed geometry of the macrocycles. The most stable

ACS Paragon Plus Environment

The Journal of Organic Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

optimized structures for the free base form of both the macrocycles showed absolute planar geometries without any ring inversion with mean plane deviation (MPD) values of 0.00 and 0.00 Å respectively in accordance with the NMR spectroscopic observations. The induced correspondence of rigid ethynylene-cumulene moieties leading to NIR absorption in neutral and protonated form of macrocycles are the important highlights of this manuscript. This noteworthy finding has been supported by DFT level theoretical calculations. There is an increasing pursuit in designing such NIR absorbing/emitting systems due to their immense applications in medicine and biology for recognizing and transportation of various substrates. The geometry of the novel 30 aromatic heteroannulenes shows promise for evolution of such novel systems in near future.

TOC GRAPHIC

INTRODUCTION


Page 2 of 29

Page 3 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Carbynes, the hypothetical linear allotrope of carbon have been a topic of current research from the scientific community both experimentally and among theorists.1 The fascinating properties of carbynes are based on the unusual electrical and optical nature of sp-hybridized carbon.2 Such molecules have been explored as molecular wires and switches in nanoelectronics,3 as materials for optoelectronics due to their strong, nonlinear optical response,4 or as precursors for conducting polymers.5 Recent years have witnessed an upsurge of demand in acetylene-cumulene dichotomy.6 Although acetylene-cumulene dehydroannulenes have received much attention owing to the work of Nakagawa et al.7 the employment of acetylene-cumulene structural units in the design of porphyrins are limited and expanded porphyrins

9

8

with ethynylene-cumulene structural units are rare.10 The batho-

and hyperchromic effects brought about by core expansion of planar expanded porphyrins

11

prompted us to explore whether such effects would also occur upon inclusion of ethynylenecumulene moieties in the conjugation pathways of expanded porphyrins. It was envisaged that controlled modifications of the basic-framework of ring expanded heteroannulenes based on “mixed and matched” precursor heterocyclic subunits, and/or a reshuffling of heterocycles connectivity within macrocycle could result in systematic variations of the optical properties making them efficient NIR dyes in specific instances.12 Designing such NIR absorbing and/or emitting systems is of considerable interest due to their immense biomedical applications such as tissue diagnostics, photodynamic therapy dyes and microscopic imaging agents.

13

Recently, we reported a [40]annulenoid octaphyrin (1.2.1.1.1.2.1.1) macrocycle containing two conjugated ethynylene bridges and its [38]- annulenoid oxidized form displaying residual macrocyclic ring currents with a vis-NIR absorption profile strongly influenced by the redox and acid−base chemistry.10 Even though core-modified ring-expanded heteroannulenes have been intensively studied because of their suitability for various applications,

9c,11a

incorporating novel heterocyclic moieties as building blocks in rubyrin 1 (Chart 1) are



scarcer. It is worth mentioning that the original core modified meso-substituted rubyrin 1 in particular and functionalized bithiophene embedded within macrocyclic core of 2 and 3 in general have been studied towards deeper understanding of their conformation and aromaticity (Chart 1).14 This is due to the well-known fact that conformational rigidity of the macrocycles with enhanced aromaticity are basic requirement for any macrocycle to be used as optical materials. Macrocycles 1 and 2 are aromatic whereas macrocycle 3 is nonaromatic due to open form of dithienylethene unit where two thiophene units are linked at their positions through a cyclopentene moiety and hence interrupting the conjugation pathway. The subtle nature of these structural changes is not completely understood yet and hence there is an upsurge of demand for the synthesis of more structural variants. One such structural unit which allows systematic analysis of the importance of alignment of the -electrons is provided by the cumulenes in which -lobes of alternate C=C bonds lie in mutually perpendicular planes. To the best of our knowledge, there is no report in literature known so far where an ethynylene-cumulene moiety has been embedded in the macrocycle core of parent rubyrin 1. It was thus this consequence of our interest to study whether and how employment of ethynylene-cumulene structural units as building blocks in the development of novel porphyrinoids would modify the conformation and electronic properties of the new macrocycle. The results of such studies are reported herein and provide clues for the further development of new macrocycles with fine-tuned properties.

Chart 1. Examples of Rubyrins appended with Functionalized bithiophene moieties RESULTS AND DISCUSSION


Page 4 of 29

Page 5 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


As outlined in Scheme S1, in the first step of our synthesis, 2-iodothiophene was reacted with trimethylsilylacetylene according to a literature procedure to yield 1,2-di (thiophene-2yl)ethyne 4.15 Further reacting this bithiophene with n-butyllithium and mesitaldehyde/ptolualdehyde gave the desired bithiophenediol 5/6. As outlined in Scheme 1, the new macrocycles have been synthesized by acid catalyzed Lindsey type condensation of bithiophenediol and pyrrole using BF3.Et2O followed by oxidation with chloranil.12a Column chromatographic separation over basic alumina followed by repeated silica gel (200-400 mesh) chromatographic separation yielded 10 % of macrocycle 7 and 7% of macrocycle 8 as air-stable green solids. The best yield was obtained with 0.1 equiv BF3.Et2O as the catalyst.

Scheme 1. Synthesis of macrocycles 7 and 8. Reagents and conditions: (a) 1. TMEDA, nBuLi, THF; 2. Ar-CHO, (b) 1. Pyrrole, BF3.Et2O, DCM; 2. chloranil

The new macrocycles have been thoroughly characterized via various spectroscopic techniques and in depth theoretical calculations. The elemental composition of 7 and 8 was confirmed by positive-mode MALDI-TOF mass spectrometry, which showed the parent ion peak at m/z 1028.451 for 7 and 918.515 for 8 (Figure S4 and Figure S5). It is well-known that the extent of electronic delocalization and communication is very important when ethynylene spacers are used. Figure 1 shows the UV-vis-NIR spectra of the free base and protonated forms of 7 and 8. The fully conjugated aromatic nature of the macrocycles both



for the free bases in neutral conditions and the dications upon protonation, is supported by the UV-vis-NIR spectral pattern. As the free base, macrocycle 7 exhibits two relatively strong Soret absorptions at 540 nm and 577 nm followed by distinct intense Q-type absorption at 800 nm and a weak Q-type absorption band at 950 nm. The electronic absorption spectrum of 8 is indeed extremely similar in shape and structure to the spectrum of 7 with intense Soret like bands at 515 nm and 540 nm followed by distinct intense Q-type absorption at 735 nm and meagrely intense Q-type absorption band at 940 nm. These features engender typical porphyrinic nature16 that would be expected for a highly delocalized, conjugated system potentially corresponding to an aromatic [30]system

Figure 1. (A) UV-vis absorption spectra of (a) 7 as the free base and upon protonation with TFA in CH2Cl2 at 298 K; (b) 8 as the free base and upon protonation with TFA in CH2Cl2 at 298 K. with -electron communication mediated by "ethynylene-cumulene" moieties. The bathochromic shifts in macrocycle 7 compared to 8 both in Soret band region and Q-type band are a consequence of more rigid structure due to steric effect by meso-mesityl substituents in 7. Upon protonation, the Soret band appears at 648 nm and an intense Q-type band at 1089 nm for macrocycle [7-H2]2+ and Soret band at 598 nm followed by intense Qtype band at 975 nm for macrocycle [8-H2]2+. These effects are due to an increased conjugation upon protonation which complements the already rich literature on expanded


Page 6 of 29

Page 7 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


porphyrins with structural diversities and aromaticity.17 The absorption spectra changed gradually but distinctly on varying the temperature, in accordance with the fact that conformational flexibility and complexity is more apparent for expanded porphyrins.11 The Soret-like band experiences minor red shift with increasing intensity and the Q-bands are also slightly more intense upon lowering the temperature, whereas increasing the temperature has a reverse effect on the UV-vis spectral pattern (Figure S7 and Figure S8). These spectral changes indicate that lowering the temperature caused an increase in aromatic character. In conjunction with electronic absorption spectral pattern, proton NMR spectroscopic analysis of the macrocycle 7 revealed the presence of an apparent sustained diamagnetic ring current ascribable to aromatic macrocycle through a [30] electronic delocalization motif in

Figure 2. (A) 1H NMR Spectral pattern in neutral and in protonated form of 7 in CD2Cl2 at 268 K; (B) 1H -13C HSQC spectra of neutral (blue) and protonated (red) in CD2Cl2 at 268 K. (C) Stack plot of VT 1H NMR Spectral pattern in protonated form of 7 in CD2Cl2; (D) 1H-13C HSQC (red) and HMBC (blue) spectra overlay of pyrrole -CH of protonated form in CD2Cl2 at 268 K. (E) HMBC spectra of pyrrole -NH in CD2Cl2 at 263 K.



free base as well as in protonated form. These later revealed the typical downfield resonances of the -pyrrolic and -thiophene protons and up field resonance for inner NH. The 1H NMR spectral patterns upon lowering the temperature (Figure S16) provided an insight into structural rigidity with very nearly planar macrocyclic framework without any conceivable conformational fluxionality. At 268 K in CD2Cl2, the 1H-NMR spectrum of the free base form exhibited spectral features that are consistent with the maximum attainable symmetry of the molecular framework. In, the 2D COSY spectra (Figure S17), a pair of doublets at 10.06 and 11.13 ppm exhibited bond correlation, thus have been assigned as β-thiophene -CH protons. In the 2D NOESY spectra (Figure S18), the sharp singlet at 7.50 ppm exhibits correlations with two signals at 2.10 and 2.75 ppm, thus the former signal has been unequivocally assigned as meso-mesityl –CH peak and the later signals as o-Me and p-Me respectively. The singlet at 8.71 ppm exhibited no correlations with any other peaks in the 2D COSY and NOESY spectra, thus has been assigned as pyrrole -CH protons. Further confirmations of all the assigned signals have been corroborated based on 1H-13C HSQC and HMBC spectra (Figure S21). It must be emphasized here that due to poor solubility of free base form of macrocycle 7 in CD2Cl2, the correlations for thiophene -CH protons in the HMBC spectra could not be observed. Extreme insolubility of free base 8 made the recording of 1H NMR extraordinarily difficult. Titration of macrocycle 7 with trifluoroacetic acid (TFA-d) in CD2Cl2 performed at ambient temperature under

1H

NMR control revealed the formation of well-defined

protonated form. A solution of 5% TFA-d in CD2Cl2 was made and aliquots of 20L were added to the CD2Cl2 solution of 7. The first addition showed maximum shift indicating protonation increasing solubility and further addition led to signal broadening (Figure S23) due to slow exchange between mono [7-H]+ and diprotonated species [7-H2]2+ (up to 100 L addition). Signals were narrowed on further additions without any change in chemical shift


Page 8 of 29

Page 9 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(Figure S23). Upon lowering the temperature to 268 K, we could arrive at an assignable spectra where the –NH signals appeared. This broad signal at -7.5 ppm slowly appeared as a sharp signal upon further lowering the temperature to 238 K (Figure 2C) mostly due to slowing down of exchange with deuterium of TFA-d whereas temperature dependent appreciable spectral changes in the aromatic and methyl region were not observed (Figure S24). In the 2D NOESY spectra (Figure S26), at 268 K, the methyl peak at 2.09 ppm exhibited strong cross peaks to the adjacent proton at 7.8 ppm and weak cross peaks to signals at 10.17 ppm and 11.47 ppm. This stipulates the peak at 2.11 ppm as o-Me, the peak at 7.8 ppm as mesityl -CH, the signal at 10.17 ppm as -CH of pyrrole and the signal at 11.47 ppm as -CH of thiophene ring respectively. In 2D COSY spectra (Figure S25), the peak at 11.47 ppm exhibits cross peak with the peak at 12.5 ppm accounting for the later peak as the -CH of thiophene ring adjacent to "ethynylene-cumulene" conjugate. The signal at -7.19 ppm has been unequivocally assigned as –NH peak. The assignment is corroborated by the observed correlations in HSQC (Figure 2D) and HMBC (Figure 2E) spectra. In the HSQC spectra, pyrrole CH shows correlation to quaternary carbon at ~140 ppm (Figure 2B). In the HMBC spectra of pyrrole NH (Figure 2E) recorded at 268 K, a correlation between the signal at -7.5 ppm to pyrrole carbon at ~132 ppm and another to pyrrole quaternary carbon at ~140 ppm has been observed and thus confirming the signal at -7.5 ppm as NH peak. In the

13C

NMR spectra (Figure S27), observation of only one peak at 111.11 ppm has been attributed to the Kekulé resonance structure having ethynylene and cumulene bonds (Csp

Csp).8a

Overall, protonation induced enhanced aromaticity has been witnessed in the 1H and

13C

chemical shifts of the aromatic CH groups and methyl groups and appearance of NH peak at 7.5 ppm with  value (difference in chemical shift between inner NH/CH and outer NH/CH protons in 1H NMR spectrum) of 20 ppm.18 Taken together, these spectroscopic data speak for the planar aromatic nature of 7 both in neutral and protonated form [7-H2]2+.



For macrocycle 8, upon protonation using 10% CF3COOH/CD2Cl2 (Figure S31) and lowering the temperature to 243 K (Figure S32), we could arrive at well assigned spectra. The signal at -3.74 ppm has been assigned to –NH signal. Unfortunately, no scalar coupling between this signal with any signals in deshielded region were observed in 2D COSY spectra. In the 2D COSY spectra (Figure S33), the correlation between signals at 2.37 ppm with broad signal at 7.8 ppm clearly indicates the signals in aromatic zone correspond to meso-tolyl CHs. This later signal in turn exhibited bond correlation with the peak at 7.6 ppm accounting for this peak as o-CHs of meso-tolyl substituents. In the 2D COSY spectra, the broad signal at 10.25 ppm exhibited scalar coupling with the peak at 9.81 ppm unequivocally accounting these signals as outer -CHs of thiophene rings. In the deshielded zone, the signal at 10.15 ppm that exhibited no scalar and dipolar coupling to any peaks in the shielded and deshielded region has been unambiguously assigned to the outer -CHs of pyrrole rings. The calculated  value from chemical shift is found to be 14.10 ppm, thus suggesting aromaticity in this macrocycle. The smaller  value in the macrocycle 8 compared to 7 is due to the fact that meso-mesityl substituents impart more structural rigidity to the macrocycle 7 compared to more flexible meso-tolyl in 8 as discussed in the absorption spectra. For macrocycles 7 and 8, failure to obtain a good single crystal suitable for X-ray diffraction in free base form and/or protonated form forced us to resort to geometry optimization based on 1H NMR spectra to arrive at the proposed structure of the macrocycles on DFT-formalism.19 Figure 3 summarizes all plausible conformers for macrocycles 7 and 8


Page 10 of 29

Page 11 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. Key geometrical parameters and relative free energies (kcal/mol) for the possible conformers of optimized coordinates of free base form of 7 and 8 at B3LYP/6311++G(d,p)//B3LYP/6-31G(d,p) level of theory. where the possibility for heterocyclic ring inversion has been thoroughly envisaged. The conformations with inverted thiophene rings have been found to be thermodynamically less stable. The most stable optimized structures of free base 7 and 8 showed absolute planar geometries without any ring inversion with mean plane deviation (MPD) values of 0.00 and 0.00 Å respectively in accordance with the NMR spectroscopic observations. Moreover, the C-C bond length of 1.234Å and 1.376Å at the ethynylene linker site are closer to cumulene like structure.20,

4d

Whereas the Wiberg bond index obtained from the natural bond orbital

analysis19c indicates 2.4 bond order for the ethynylene units of 7 and 8 and 1.3 bond order for



the adjacent bonds indicating a delocalized Csp

Csp bonds at the linkers that is extended

to macrocycles. Taking into account the geometrical and bonding properties of macrocycles 7 and 8, it strongly indicates a resonance hybrid structure that is fully conjugated. We also obtained optimized structures of protonated [7-H2]2+ and [8-H2]2+. Compared to freebase 7 and 8, the protonated [7-H2]2+ and [8-H2]2+ exhibited more distorted structures due to the steric repulsion between pyrrolic protons with sulfur lone pairs that has resulted in puckering of the ring and pushing the pyrrolic protons above the plane (15.7˚ and 12.8˚ for protonated [7-H2]2+ and [8-H2]2+ respectively with respect to the atoms of mean plane of the macrocycles). It is noted that the dihedral angles of meso-mesityl substituents 77.9˚ are larger than those of meso-tolyl substituents 48.2˚, reflecting the larger steric effect of mesityl substituents on the macrocycle along with their MPD values. In order to gain an insight into the origin of intense NIR absorption bands of 7 and 8, we performed TD-DFT calculations at the B3LYP-6-31G (d, p) level of theory. The simulated UV-vis spectra in presence of dichloromethane for 7 and 8 were found to coincide with the steady-state absorption spectra (Figure S36 and Figure S39). On the basis of calculations, the electronic vertical transitions corresponding to the two Soret-like bands, the sharp Q-type band observed in the steady-state absorption spectra of 7 and 8 mainly involve HOMO-1, LUMO, LUMO+1 orbitals (Table S2 and S5). These orbitals are all characterized with delocalized -electron densities through 30-electronic circuit formed due to mixing of  orbitals of cumulene fragment with the  orbitals of thiophene and pyrrole rings. Figure 4 depicts the nature of  orbitals present in the cumulene (HOMO, LUMO) is also observed in the FMO region of 4 where it shows the delocalization of  electron cloud from cumulene to thiophene ring as observed in 7 and 8. This indicates that planar nature of macrocycle with extended delocalized -electron densities tremendously lowered the HOMO-LUMO gap by 0.4-0.44 ev compared to 1 and enhanced the absorption of light to NIR region. This is due to the ethynylene-cumulene linker


Page 12 of 29

Page 13 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


increasing conformational rigidity of the macrocycles. On a similar note, upon protonation, the number of bands in visible region mainly involves delocalized  orbitals (Figure S38 and Figure S41) while the NIR bands are mere consequence of cumulene type orbitals delocalized with -electrons of macrocyclic ring that is predominant in HOMO and LUMO (Figure 4, Table S4 and S7).

Figure 4. Frontier orbitals of cumulene (A), 4(B), free base form of 7(C) and free base form of 8 (D). Note that π orbitals of cumulene delocalize with thiophene π orbital in 4 and further gets extended to pyrrole rings forming a 30 π electron cloud in 7 and 8.



To gain deeper insight into the aromaticity of 7 and 8, we conducted NucleusIndependent Chemical shift (NICS) 21 calculation. In line with the 1H NMR spectra of 7 and 8, their NICS values at the center of the macrocycles were estimated to be -15.316 and 15.212 ppm respectively, indicating the aromatic character. In the protonated form, macrocycles [7-H2]2+ and [8-H2]2+ exhibit NICS values -15.090 and -13.117 ppm respectively (Figure S43). Additionally, this aromatic character has been clearly illustrated by Anisotropy of the Induced Current Density (ACID) plots, 22 where the distinct clockwise ring currents of freebase and protonated 7 and 8 visualized their aromatic nature (Figure S42). Furthermore, the estimated Harmonic Oscillator Model of Aromaticiy (HOMA) 23 values of 0.860, 0.801 for free base 7 and 8 and degenerate frontier molecular orbital (FMOs) with energy level diagrams (Figure S44) are well matched with their aromatic nature.

Figure 5. Cyclic Voltamomogram of 7 The macrocycles 7 and 8 have been found to be robust against electrochemical oxidation and reduction. Electrochemical properties of the new macrocycle were probed with cyclic voltammetry in dichloromethane using 0.1M tetrabutylammoniumhexafluorophosphate as a supporting electrolyte. The macrocycle 7 exhibits two irreversible waves for oxidation process at 0.52 V and 0.91 V. Two quasireversible reduction peaks were detected at ca. −0.75 V and -0.92 V yielding an estimate of the electrochemical HOMO−LUMO gap (HLG) of


Page 14 of 29

Page 15 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1.27 V (Figure 5). As expected of an expanded porphyrinoid, the latter value is considerably reduced relative to meso-tetraphenylporphyrin (2.26 V).24 To the extent this energy difference, E1/2 , represents the energy gap between the highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbitals of the macrocycle, it reflects ethynylenecumulene modality of this macrocycle. For macrocycle 8, electrochemical studies could not be carried out due to very low solubility in any organic solvent. CONCLUSION

In conclusion, we have successfully synthesized and thoroughly characterized first ever ethynylene-cumulene conjugated expanded aromatic [30] heteroannulenes from easy to make precursors. The propensity of these macrocycles to absorb strongly in NIR region has been well benefitted from the presence of intriguing resonance hybrid structure having rigid ethynylene-cumulene moieties (Csp

Csp). This unexpectedly large effect seemingly allows

the expanded porphyrin chromophores to be modulated to a far greater extent in their electronic absorption than previously been recognized for related heteroannulenes. These macrocycles will no doubt receive considerable attention in near future in light of their NIR absorption, finding possible applications in materials science and bio-medicine. We would anticipate a continued rich and varied chemistry in these areas in near future. EXPERIMENTAL SECTION

Materials and Methods. Electronic absorption spectra were measured using a UV-vis-NIR spectrophotometer. 1H, and 13C NMR spectra were recorded on a spectrometers (operating at 500.13/700.13 MHz for 1H and 125.77/176.05 MHz for 13C) using the residual solvents as the internal references for 1H [(CHCl3 (δ = 7.26 ppm), CH2Cl2 (δ = 5.32 ppm). MALDI-TOF MS data were recorded using Bruker Daltonics flex Analyser and ESI HR-MS data were recorded



Page 16 of 29

using Waters QTOF Micro YA263 spectrometer. Cyclic voltammograms were recorded using a platinum working electrode, a platinum wire counter electrode and a Ag/AgCl reference electrode in Bioanalytical Systems EC epsilon. The measurements were carried out in CH2Cl2 solution using 0.1 M Bu4NPF6 as the supporting electrolyte at a scan rate of 0.1 V/s. Peak potentials were determined from differential pulse voltammetry experiments. The Fc/Fc+ redox couple was used as an internal standard. All solvents and chemicals were of reagent grade quality, obtained commercially and used without further purification except as noted. For spectral measurements, anhydrous dichloromethane was obtained by refluxing and distillation over CaH2. Dry THF was obtained by refluxing and distillation over pressed Sodium metal. Thin layer chromatography (TLC) was carried out on alumina sheets coated with silica gel 60 F254 and gravity column chromatography were performed using Silica Gel 230-400 mesh. Computational chemistry. Electronic structure calculations of 7 and 8 were carried out using density functional theory (DFT) with Becke’s three-parameter hybrid exchange functional and the Lee-Yang-Parr correlation functional (B3LYP) 19 and 6-31G (d,p) basis set for all the atoms (B1).25 Further harmonic vibrational frequencies were computed on optimized geometries of free base and protonated forms of 7 and 8 to verify the nature of stationary points. To evaluate the absorption spectrum of free base and protonated form of 7 and 8 the time-dependent TD-DFT26 calculations were performed in presence of dichloromethane solvent using the polarizable continuum model (PCM) using the integral equation formalism variant (IEFPCM) 27 at B1 level of theory. Using optimized geometries, Wieberg bond index were obtaining from NBO analysis,19c NICS values were obtained with the GIAO method

28

and AICD plots were obtained with CSGT

theory. The aromatic nature of macrocycles

23

29

method at B1 level of

7 and 8 were confirmed from the negative

nucleus-independent chemical shifts (NICS)21 values and also from the magnitude and


Page 17 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


direction of current densities from Anisotropy of induced ring current density (AICD)22 plots. Also performed single point energies of most feasible conformers of 7 and 8 at B3LYP/6311++G (d,p)30 level of theory (B2) to know the thermodynamic stability in three plausible conformers of 7 and 8. Note that all these calculations were carried out using Gaussian 16 program suite. 31 SYNTHESIS 2 (2-Thienylethynyl)thiophene (4): To an oven-dried 25 mL round-bottom flask were added Pd(PPh3)2Cl2 (67.4 mg, 6 mol %), CuI (30.5 mg, 10 mol %), and 2-iodothiophene (0.17 mL, 1.6 mmol), and the flask was purged with argon. Argon-purged anhydrous toluene (8 mL) and DBU (1.43 mL, 6 equiv) were added successively by syringe. Ice-chilled trimethylsilylethyne (104.5 μL, 0.50 equiv) was then added by syringe, followed immediately by distilled water (11.5 μL, 40 mol %). The reaction flask was covered by aluminum foil and stirred for 18 h at RT. Then the reaction mixture was partitioned in ethyl ether and distilled water (50 mL each). The organic layer was washed with 10% HCl (3 × 75 mL) and saturated aqueous NaCl (75 mL) and dried over MgSO4. The crude product was purified by silica gel column chromatography using ethyl acetate – hexane (0.1:99.9) solution.

Yield: 130.9 mg, 86%, M.p. 98-100 C. 1H NMR (400 MHz, CDCl3) δ 7.27-7.31 (m, 4H), 7.00-7.02 (m, 2H).

13C{1H}NMR

(100 MHz, CDCl3) δ 132.2, 127.7, 127.2, 123.0, 86.3.

HRMS(ESI-TOF) (m/z): [M]+ Calcd for C10H6S2 189.9911; Found 189.9951. Elemental analysis: Calcd for C10H6S2: C, 63.12; H, 3.18.; S, 33.7. Found: C, 63.14; H, 3.16; S, 33.72.

1,2-Bis((5-mesitylhydroxymethyl)-2-thienyl)ethyne (5): To a 250 mL round-bottomed flask equipped with a magnetic bar, 4 (1.354 g, 7.13 mmol) was placed followed by dry THF



(40 mL). The reaction mixture was stirred under inert atmosphere. N, N, N′, N′-Tetramethyl ethylenediamine (3.2 mL, 0.021mol) was added followed by stirring for 30 min at room temperature. Afterward, n-BuLi in hexane (1.6 M) (13.04 mL, 0.021 mol) was added through rubber septa drop wise, yellow turbidity started forming. The reaction mixture was stirred at room temperature for 2 h and then heated to 66 oC for 1 h. The reaction mixture was brought to room temperature after which it was brought to ice cold temperature. At ice cold temperature, Mesitaldehyde (2.62 mL, 0.017mol) in dry THF (40 mL) was then added drop wise to the reaction mixture, the reaction mixture was stirred for 2 h. The reaction mixture was quenched by saturated NH4Cl (aq) solution, product was extracted by diethyl ether, dried over Na2SO4. The crude product was precipitated out by hexane and purified by silica gel column chromatography using the mixture of ethyl acetate - hexane (20:80) solution. The solvent was evaporated and light yellow solid was obtained. Yield 2.30g (67%). M.p. 135-137 C.

1H

NMR (500 MHz, CDCl3, 300K,  [ppm]): 1.65

(brs, 2H); 2.28(s, 6H); 2.31(s, 12H); 6.39(s, 2H); 6.52(d, 2H, J = 3.5Hz); 6.86 (s, 4H); 7.05 (d, 2H, J= 3.5 Hz). 13C{1H} NMR (125 MHz, CDCl3, 300K,  [ppm]): 20.3, 20.8, 69.3, 86.4, 122.2, 123.5, 130.0, 131.9, 135.3, 136.7, 137.8, 150.2. HRMS (ESI-TOF) m/z: [M+Na]+ Calcd for C30H30O2S2Na 509.1585; Found 509.0054. (Elemental analysis: Calcd for C30H30O2S2: C, 74.04; H, 6.21.; S, 13.18. Found: C, 74.10; H, 6.48; S, 13.20. 1,2-Bis((5-tolylhydroxymethyl)-2-thienyl)ethyne (6): To a 250 mL round-bottomed flask equipped with a magnetic bar, 4 (1.354 g, 7.13 mmol) was placed followed by dry THF (40 mL). The reaction mixture was stirred under inert atmosphere. N, N, N′, N′-Tetramethyl ethylenediamine (3.2 mL, 0.021mol) was added followed by stirring for 30 min at room temperature. Afterward, n-BuLi in hexane (1.6 M) (13.04 mL, 0.021 mol) was added through rubber septa drop wise, yellow turbidity started forming. The reaction mixture was stirred at


Page 18 of 29

Page 19 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


room temperature for 2 h and then heated to 66 oC for 1 h. The reaction mixture was brought to room temperature after which it was brought to ice cold temperature. At ice cold temperature, p-Tolualdehyde (2.00 mL, 0.017mol) in dry THF (40 mL) was then added drop wise to the reaction mixture, the reaction mixture was stirred for 2 h. The reaction mixture was quenched by saturated NH4Cl (aq) solution, product was extracted by diethyl ether, dried over Na2SO4. The crude product was precipitated out by hexane and purified by silica gel column chromatography using the mixture of ethyl acetate - hexane (1:6) solution. The solvent was evaporated and light yellow solid was obtained. Yield 1.87g (61%). M.p. 125-127 C. 1H NMR (500 MHz, CDCl3, 300K,  [ppm]): 2.28 (s, 6H); 6.29 (s, 2H); 6.52 (d, 2H, J = 3.5 Hz); 6.78 (d, 4H, J= 8 Hz); 6.83 (d, 4H, J= 8 Hz); 7.08 (d, 2H, J= 3.5 Hz).

13C{1H}

NMR (125 MHz, CDCl3, 300K,  [ppm]): 21.8, 67.3, 84.4,

122.2, 123.5, 130.0, 131.9, 135.3, 136.7, 137.8, 150.2. HRMS (ESI-TOF) (m/z): [M+] Calcd for C26H22O2S2 430.1061; Found 430.1847. Elemental analysis: Calcd for C26H22O2S2: C, 72.53; H, 5.15.; S, 14.89. Found: C, 72.39; H, 5.48; S, 14.83. Synthetic procedure of Compound 7: Under nitrogen atmosphere and in dark condition a solution of 534 mg of compound 5 (486 mg, 1 mmol) and freshly distilled pyrrole (0.07 mL, 1 mmol) in 250 mL dry dichloromethane was stirred for 30 minutes. Afterward, catalytic amount of BF3.Et2O (0.1 mL) was added to the reaction mixture and stirred at RT for 90 minutes. Then chloranil (614 mg, 2.5 mmol) was added and opened to air and the mixture was refluxed for another 1 h. The solvent was removed under reduced pressure and compound was filtered by basic alumina followed by repeated silica gel column chromatography with the mixture of 1% methanol - dichloromethane solution. After recrystallization, the title compound was yielded as dark green crystals.



Yield. ~101mg (~10%). M.p.> 300 °C. MALDI-TOF MS (m/z): 1028.451 (Calc. for C68H56N2S4 exact mass: 1028.3326). Elemental analysis: Calcd for C68H56N2S4: C, 79.34; H, 5.48.; N, 2.72.; S, 12.46. Found: C, 80.01; H, 5.55; N, 2.70. UV-vis (CH2Cl2, λ [nm], (ϵ [M-1 cm-1x105]), 298K): 540 (3.79), 577 (3.81), 800 (1.16), 950 (0.001). [(UV-vis [CF3COOH/CH2Cl2, λ [nm], (ϵ [M-1 cm-1x104]), 298K)]: 648 (3.12), 1089 (2.86). 1H

NMR (700 MHz, CD2Cl2, 268 K,  [ppm], TMS): 2.10 (s, 24H, o-CH3); 2.75 (s, 12H, p-

CH3); 7.50 (s, 8H, -CH mesityl); 8.71 (s, 4H, pyrrole -H); 10.06 (d, J = 4.2 Hz, 4H, thiophene -H); 11.13(d, J = 4.2 Hz, 4H, thiophene -H). 13C{1H} NMR (175 MHz, CD2Cl2, 263 K,  [ppm]): 21.5, 22.6, 124.9, 127.6, 128.2, 134.6, 135.2, 138.5, 138.6, 138.9. 1H

NMR (700 MHz, 5% CF3COOD/CD2Cl2, 268 K,  [ppm], TMS): -7.19 (brs, 2H, Py-NH);

2.09 (s, 24H, o-CH3); 2.94 (s, 12H, p-CH3); 7.80 (s, 8H, -CH mesityl) ; 10.17 (s, 4H, pyrrole -H); 11.47 (d, 4H, J = 4.2 Hz, thiophene -H); 12.50 (d, 4H, J = 3.5 Hz, thiophene -H). 13C{1H}

NMR (175 MHz, CD2Cl2, 268 K,  [ppm]): 21.4, 21.6, 111.1, 129.2, 129.5, 131.4,

132.7, 137.1, 139.8, 140.8, 141.2, 141.5, 142.3. Synthetic procedure of Compound 8: Under nitrogen atmosphere and in dark condition a solution of compound 6 (430 mg, 1mmol) and freshly distilled pyrrole (0.07 mL, 1 mmol) in 250 mL dry dichloromethane was stirred for 30 minutes. Afterward, catalytic amount of BF3.Et2O (0.1 mL) was added to the reaction mixture and stirred at RT for 90 minutes. Then, chloranil (614 mg, 2.5 mmol) was added and opened to air and the mixture was refluxed for another 1 h. The solvent was removed under reduced pressure and compound was filtered by basic alumina followed by repeated silica gel column chromatography with the mixture of 5% methanol - dichloromethane solution. After recrystallization, the title compound was yielded as dark green crystals.


Page 20 of 29

Page 21 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Yield. ~64 mg (~7%). M.p.> 300 °C. MALDI-TOF MS (m/z): 916.515 (Calc. for C60H40N2S4 exact mass: 916.2074). Elemental analysis: Calcd for C60H40N2S4: C, 78.57; H, 4.40.; N, 3.05.; S, 13.98. Found: C, 78.88; H, 4.45; N, 3.02.; S, 13.65. UV-VIS (CH2Cl2, λ [nm], (ϵ [M1

cm-1x105]), 298 K): 515 (3.39), 540 (3.56), 735 (1.08), 940 (0.001). [(UV-VIS

[TFA/CH2Cl2, λ [nm], (ϵ [M-1 cm-1 x 104]), 298 K)]: 530 (sh), 598 (1.16), 975 (0.78). 1H

NMR (500 MHz, 120L CF3COOH/CD2Cl2, 243 K,  [ppm], TMS): -3.74 (brs, 2H, -

NH); 2.37 (12H, p-CH3); 7.6 (brs, 8H, -CH tolyl); 7.8 (brs, 8H, CH-tolyl); 9.8 (brs, 4H, thiophene -H); 10.15 (brs, 4H, pyrrole -H); 10.25 (brs, 4H, thiophene -H). ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Scheme, Conformational dynamics of 7 and 8. HR-ESI-TOF mass spectra, MALDI-TOF mass spectra, NMR spectra (1H NMR, 1H-1H

13C

{1H} NMR, acid titration, variable temperature,

COSY, 1H-1H ROESY, HMBC, HSQC), details of absorption spectroscopic (acid

titration, variable temperature study), results of DFT calculations. ORCID Harapriya Rath: 0000-0002-5507-5275 Dandamudi Usharani: 0000-0001-5728-9421 Notes The authors declare no competing financial interest(s). ACKNOWLEDGEMENTS



KCS thanks CSIR, New Delhi for senior research fellowship. HR thanks DST-SERB (EMR/2016/004705), New Delhi, India for research grant. MS thanks CFTRI for research fellowship. DU thanks CFTRI for computing facilities. Our sincere thanks to Dr. Sapna Ravindranathan and Dr. P. R. Rajamohanan, Centre for NMR Facility, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India for their help in NMR experiments and discussion in the NMR assignment for the macrocycle 7 reported in the manuscript. REFERENCES 1. (a) Chalifoux, W. A.; Tykwinski, R. R. Synthesis of polyynes to model the sp-carbon allotrope carbine. Nature Chem. 2010, 2, 967-971. (b) Kavan, L. Electrochemical Carbon. Chem. Rev. 1997, 97, 3061-3082. (c) Baughman, R. H. Dangerously Seeking linear Carbon. Science, 2006, 312, 1009-1110. 2. (a) Hendon, C. H.; Tiana, D.; Murray, A. T.; Carbery, D. R.; Walsh, A. Helical Frontier Orbitals of Conjugated Linear Molecules. Chem. Sci. 2013, 4, 4278-4284. (b) Usanmaz, D.; Srivastava, G. P. Progressive structural and electronic properties of nano-structured carbon atomic chains. J. Appl. Phys. 2013, 113, 193704-1-193704-6. (c) Mölder, U.; Burk, P.; Koppel, I. A. Quantum chemical calculation of linear cumulene chains. THEOCHEM. 2004, 712, 81-89. (d) Podkopaeva, O. Yu.; Chizhov, Yu. V. DFT study of the geometrical and electronic structure of substituted cumulenes in neutral and cationic forms. J. Struct. Chem. 2006, 47, 420-426. 3. Liu, M.; Artyukhov, V. I.; Lee, H.; Xu, F.; Yakobson, B. I. Carbyne from First Principles: Chain of C Atoms, a Nanorod or a Nanorope. ACS Nano. 2013, 7, 10075-10082. 4. (a) Eisler, S.; Slepkov, A. D.; Elliott, E.; Luu, T.; McDonald, R.; Hegmann, F. A.; Tykwinski, R. R. Polyynes as a Model for Carbyne: Synthesis, Physical Properties, and Nonlinear Optical Response. J. Am. Chem. Soc. 2005, 127, 2666-2676. (b) Lucotti, A.;


Page 22 of 29

Page 23 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Tommasini, M.; Fazzi, D.; Zoppo, M. Del.; Chalifoux, W. A.; Tykwinski, R. R.; Zerbi, G. J. Raman Spectrosc. 2012, 43, 1293-1298. (c) Kminek, I.; Klimovic, J.; Prasad, P. N. Thirdorder nonlinear optical response of some tetrasubstituted cumulenes. Chem. Mater. 1993, 5, 357-360. (d) Januszewski, J. A.; Tykwinski, R. R. Synthesis and properties of long [n]cumulenes (n > 5). Chem. Soc. Rev. 2014, 43, 3184-3203. 5. Shirakawa, H.; Louis, E.J.; MacDiarmid, A.G.; Chiang, C.K.; Heeger, A. J. Synthesis of electrically conducting organic polymers: halogen derivatives of polyacetylene, (CH)x. J. Chem. Soc. Chem. Commun. 1977, 0, 578-580. 6. (a) Milani, A.; Lucotti, V.; Russo, M.; Tommasini, F.; Cataldo, A.; Bassi, L.; Casari, C. S. Charge Transfer and Vibrational Structure of sp-Hybridized Carbon Atomic Wires Probed by Surface Enhanced Raman Spectroscopy. J. Phys. Chem. C, 2011, 115, 12836-12843. (b) Weimer, M.; Hieringer, W.; Della Sala, F.; Gorling, A. Electronic and optical properties of functionalized carbon chains with the localized Hartree–Fock and conventional Kohn–Sham methods. Chem. Phys. 2005, 309, 77-87. 7. (a) Sondhiemer, F. Recent advances in the chemistry of large-ring conjugated systems. Pure Appl. Chem. 1963, 7, 363-388. and references therein. (b) Fukui, K.; Nomoto, T.; Takatsuki, S.; Nakagawa, M. 3, 7, 10, 14-tetrasubstituted 1, 8-didehydro[14]annulens. Tetrahedron Lett. 1972, 3157-3160. (c) Iyoda, M.; Nakagawa, M. 3,9,12,18-tetra-t-butyl- and 3,12-di-t-butyl-9,18-diphenyl-1,10-didehydro[18]annulenes. Tetrahedron Lett. 1972, 31613164. (d) Nakagawa, M. Acetylene-Cumulene dehydroannulenes. Pure Appl. Chem. 1975, 44, 885-922. (e) Kabuto, M. C.; Kitahara, Y.; Iyoda, M.; Nakagawa, M. The crystal and molecular structure of 3, 11, 14, 22-tetra-t-butyl-didehydro[22]annulene. Tetrahedron Lett. 1976, 2787-2790. (f) Nakagawa, M. Annulenoannulenes. Angew. Chem. Int. Ed. Engl. 1979, 18, 202-214.



Page 24 of 29

8. (a) Jux, N.; Koch, P.; Schmickler, H.; Lex, J.; Vogel, E. Acetylene-cumulene Porphyrinoids. Angew. Chem. Int. Ed. 1990, 29, 1385-1387. (b) Mirtire, D. O.; Jux, N.; Aramendia, P. F.; Negri, R. M.; Lex, J.; Braslavsky, S. E.; Schaffner, K.; Vogel, E. Photophysics and photochemistry of 22 and 26 Acetylene-cumulene porphyrinoids. J. Am. Chem. Soc. 1992, 114, 9969-9978. (c) Anderson, S.; Anderson, H. L.; Sanders, J.K.M. Expanding roles for Templates in Synthesis. Acc. Chem. Res. 1993, 26, 469-475. (d) Ueta, K.;

Naoda,

K.;

Ooi,

S.;

Tanaka,

T.;

Osuka,

A.

meso‐Cumulenic 2H‐Corroles

from meso‐Ethynyl‐3H‐corroles. Angew. Chem. Int. Ed. 2017, 56, 7223-7226. (e) Walter, V.; Gao, Y.; Grzegorzek, N.; Krempe, M.; Hampel, F.; Jux, N.; Tykwinski, R. R. Building from Ga‐Porphyrins: Synthesis of Ga‐Acetylide Complexes Using Acetylenes and Polyynes. Angew. Chem. Int. Ed. 2019, 58, 494-498. (f) Vogel, E.; Jux, N.; Dörr, J.; Pelster, T.; Berg, T.; Böhm, H.-S.; Behrens, F.; Lex, J.; Bremm, D.; Hohlneicher, G. Furan based Porphyrins: Tetraoxa [4n+2]Porphyrin Dications with 18p, 22p, or 26p Electron Systems. Angew. Chem. Int. Ed. 2000, 39, 1101-1105. (g) Kurata, H.; Baba, H.; Oda, M. 5,8,17,20-Tetrakis(3,5-di-tbutylphenyl)-6,7,18,19-tetradehydrotetrathia[24]annulene-(4.0.4.0) and Its Dianion: New Thiophene-Derived Paratropic and Diatropic Annulenes. Chem. Lett. 1997, 25, 571-572. 9. (a) Sessler, J. L.; Weghorn, S. J. Expanded, Contracted and Isomeric Porphyrins, Pergamon, New York, 1997, 15, 429. (b) Jasat, A.; Dolphin, D. Expanded porphyrins and their Heterologs. Chem. Rev. 1997, 97, 2267-2340. (c) Chandrashekar T. K.; Misra, R. Structural Diversity in Expanded Porphyrins. Acc. Chem. Res. 2008, 41, 265-279. (d) Stępień, M.; Sprutta, N.; Latos-Grażyński, L. Figure Eights, Möbius Bands, and More: Conformation and Aromaticity of Porphyrinoids. Angew. Chem. Int. Ed. 2011, 50, 4288-4340.


Page 25 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


10. Sahoo, K. C.; Majewski, M.A.; Stępień, M.; Rath, H. Ethynylene-linked Figure-eight Octaphyrin(1.2.1.1.1.2.1.1): Synthesis and Characterization of Its Two Oxidation States. J. Org. Chem. 2017, 82, 8317-8322. 11. (a) Chandrashekar, T. K.; Venkataraman, S. Core-modified Expanded Porphyrins: New Generation Organic Materials. Acc. Chem. Res. 2003, 36, 676-691. (b) Saito, S.; Osuka, A. Expanded Porphyrins: Intriguing Structures, Electronic Properties, and Reactivities. Angew. Chem. Int. Ed. 2011, 50, 4342-4373. 12. (a) Rath, H.; Mallick, A.; Ghosh, T.; Kalita, A. Aromatic fused heterocyclic [22] macrocycles with NIR absorption. Chem. Commun. 2014, 50, 9094-9096. (b) Mallick, A.; Oh, J.; Kim, D.; Rath, H. Aromatic Fused [30] Heteroannulenes with NIR Absorption and NIR Emission: Synthesis, Characterization and Excited State Dynamics. Chem. Eur. J. 2016, 22, 8026-8031. (c) Shin, J. -Y.; Furuta, H.; Osuka, A. N-Fused Pentaphyrin. Angew. Chem. Int. Ed. 2001, 40, 619-621. (d) Lash, T. D. Modification of the Porphyrin Chromophore by Ring Fusion: Identifying Trends due to Annelation of the Porphyrin. J. Porphyrin and Phthalocyanines, 2001, 5, 267-288. (e) Panda, P. K.; Kang, Y. -J.; Lee, C. -H. A Benzodipyrrole‐Derived Sapphyrin. Angew. Chem. Int. Ed. 2005, 44, 4053-4055. (f) Wu, D.; Descalzo, A. B.; Emmerling, F.; Shen, Z.; You, X. -Z. A Core-Modified Rubyrin with mesoAryl Substituents and Phenanthrene-Fused Pyrrole Rings: A Highly Conjugated NearInfrared Dye and Hg2+ Probe. Angew. Chem. Int. Ed. 2008, 47, 193-197. (g) Chang, Y.; Chen, H.; Zhou, Z.; Zhang, Y.; Schutt, C.; Herges, R.; Shen, Z. A 20-Electron Heteroporphyrin Containing a Thienopyrrole Unit. Angew. Chem. Int. Ed. 2012, 51, 12801-12805. (h) Mori, H.; Tanaka, T.; Osuka, A. Fused porphyrinoids as promising near-infrared absorbing dyes. J. Mater. Chem. C, 2013, 1, 2500-2519. (i) Anguera, G.; Cha, W.-Y.; Moore, M.D.; Brewster II, J. T.; Zhao, M. Y.; Lynch, V. D.; Kim, D.; Sessler, J. L. An Expanded Porphycene with



High NIR Absorptivity That Stabilizes Two Different Kinds of Metal Complexes. Angew. Chem. Int. Ed. 2018, 57, 2575-2579. 13. (a) Waignright, M. Therapeutic applications of near-infrared dyes. Color. Technol. 2010, 126, 115-126. (b) Pawlicki, M.; Collins, H. A.; Denning, R.G.; Anderson, H. L. Two-photon Absorption and the design of Two-photon Dyes. Angew. Chem. Int. Ed. 2009, 48, 3244-3266. (c) Carr, J. A.; Franke, D.; Caram, J. R.; Perkinson, C. F.; Saif, M.; Askoxylakis, V.; Datta, M.; Fukumura, D.; Jain, R. K.; Bawendi, M. G. Bruns, O. T. Shortwave Infrared Fluorescence imaging with clinically approved near-infrared dye indocyanine green. Proc. Natl. Acad. Sci. USA. 2018, 115, 4465-4470. and references therein. 14. Srinivasan, A.; Reddy, V. R. M.; Narayanan, S. J.; Sridevi, B.; Pushpan, S. K.; Ravikumar, M.; Chandrashekar. T. K. Tetrathia- and Tetraoxa-rubyrins: Aromatic, CoreModified, Expanded Porphyrins. Angew. Chem. Int. Ed. Engl. 1997, 36, 2598-2601. (b) Chandrashekar, T. K.; Prabhuraja, V.; Gokulnath, S.; Sabarinathana, R.; Srinivasan, A. Fused core-modified meso-aryl expanded porphyrins. Chem. Commun. 2010, 46, 5915-5917. (c) Zhou, Z.; Chang, Y.; Shimizu, S.; Mack, J.; Schutt, C.; Herges, R.; Shen, Z.; Kobayashi, N. Core modified rubyrins Containing Dithienylethene Moieties. Angew. Chem. Int. Ed. 2014, 53, 6563-6567. 15. Mio, M. J.; Kopel, L. C.; Braun, J. B.; Gadzikwa, T. L.; Hull, K. L.; Brisbois, R. G.; Markworth, C. J. Grieco, P. A. One-Pot Synthesis of Symmetrical and Unsymmetrical Bisarylethynes by a Modification of the Sonogashira Coupling Reaction. Org. Lett. 2002, 4, 3199-3202. 16. Gouterman, M. Spectra of porphyrins: Part II. Four orbital model. J. Mol. Spectrosc. 1963, 11, 108-127.


Page 26 of 29

Page 27 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


17. Saito, S.; Osuka, A. Expanded Porphyrins and aromaticity. Chem. Commun. 2011, 47, 4330-4339. 18. Franck, B.; Nonn, A. Novel Porphyrinoids for Chemistry and Medicine by Biomimetic Syntheses. Angew. Chem. Int. Ed. 1995, 34, 1795-1811. 19. (a) Becke, A. D. J. A new mixing of Hartree-Fock and local density-functional theories. J. Chem. Phys. 1993, 98, 1372-1377. (b) Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Phys. Rev. B, 1988, 37, 785-789. (c) Glendening, E. D.; Reed, A. E.; Carpenter, J. E.; Weinhold, F. NBO Version 3.1. 20. Hoffman, R. Extended Hückel Theory –v: Cumulenes, Polyenes, Polyacetylenes and Cn Tetrahedron. 1966, 22, 521-538. 21. Schleyer, P. V. R.; Maerker, C.; Dransfeld, A.; Jiao, H.; Hommea, N. J. R. V. E. NucleusIndependent Chemical Shifts: A Simple and Efficient Aromaticity Probe. J. Am. Chem. Soc. 1996, 118, 6317-6318. 22. Geuenich, D.; Hess, K.; Köhler, F.; Herges, R. Anisotropy of the Induced Current Density (ACID), a General Method To Quantify and Visualize Electronic Delocalization. Chem. Rev. 2005, 105, 3758-3772. 23. (a) Krygowski, T. M. Crystallographic studies of inter- and intramolecular interactions reflected in aromatic character of -electron systems. J. Chem. Inf. Comut. Sci. 1993, 33, 7778. (b) Krygowski, T. M.; Cryański, K. M. Structural Aspects of Aromaticity. Chem. Rev. 2001, 101, 1385-1420.



24. Kadish, K. M. The Electrochemistry of Metalloporphyrins in Nonaqueous Media. Prog. Inorg. Chem. 1986, 34, 435-605. 25. (a) Petersson, G. A.; Bennett, A.; Tensfeldt, T. G.; Al-Laham, M. A.; Shirley, W.; Mantzaris, A. J. A complete basis set model chemistry. I. The total energies of closed-shell atoms and hydrides of the first-row elements. J. Chem. Phys. 1988, 89, 2193-2218. (b) Petersson, G. A.; Al-Laham, M. A. A complete basis set model chemistry. II. Open‐shell systems and the total energies of the first‐row atoms. J. Chem. Phys. 1991, 94, 6081-6090. 26. (a) Scalmani, G.; Frisch, M. J.; Mennucci, B.; Tomasi, J.; Cammi, R.; Barone, V. Geometries and properties of excited states in the gas phase and in solution: theory and application of a time-dependent density functional theory polarizable continuum model. J. Chem. Phys. 2006, 124, 094107: 1-15. (b) Adamo, C.; Jacquemin, D. The calculations of excited-state properties with Time-Dependent Density Functional Theory. Chem. Soc. Rev. 2013, 42, 845-856. 27. (a) Miertuš, S.; Tomasi, J.; Approximate evaluations of the electrostatic free energy and internal energy changes in solution processes. J. Chem. Phys. 1982, 65, 239-245. (b) Cossi, M.; Barone, V. Solvent effect on vertical electronic transitions by the polarizable continuum model. J. Chem. Phys. 2000, 112, 2427-2435. 28. (a) Wolinski, K.; Hilton, J. F.; Pulay, P. Efficient implementation of the gaugeindependent atomic orbital method for NMR chemical shift calculations. J. Am. Chem. Soc. 1990, 112, 8251-8260. (b) London, F. J. Phys. Radium, 1937, 8, 397-409. 29. (a) Cheeseman, J. R.; Trucks, G. W.; Keith, T. A.; Frisch, M. J. A Comparison of Models for Calculating Nuclear Magnetic Resonance Shielding Tensors. J. Chem. Phys. 1996, 104, 5497-5509. (b) Keith, T. A.; Bader, R. F. W. Calculation of magnetic response properties using a continuous set of gauge transformations. Chem. Phys. Lett. 1993, 210, 223-231.


Page 28 of 29

Page 29 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


30. (a) Wachters, A. J. H. Gaussian Basis Set for Molecular Wave functions Containing Third-Row Atoms. J. Chem. Phys. 1970, 52, 1033-1036. (b) Hay, P. J. Gaussian basis sets for molecular calculations: Representation of 3d orbitals in transition-metal atoms. J. Chem. Phys. 1977, 66, 4377-4384. 31. Gaussian 16, Revision A.03, Frisch, M. J et al. Gaussian, Inc., Wallingford CT, 2016.


Conformationally Rigid EthynyleneâCumulene Conjugated Aromatic

Recommend Documents

Conformationally Rigid EthynyleneâCumulene Conjugated Aromatic